FULL PRODUCT VERSION :
java version "1.8.0_102"
Java(TM) SE Runtime Environment (build 1.8.0_102-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.10586]

A DESCRIPTION OF THE PROBLEM :
When optimistic types and persistent code caching are enabled an NPE may be thrown when type specialization results in a reparse of the function source on any but the first run / JVM execution.

If and when a NPE is triggered appears to depend on the specific content / complexity of the script and how it is loaded.

REGRESSION. Last worked in version 8u77

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_102"
Java(TM) SE Runtime Environment (build 1.8.0_102-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)

previous:
java version "1.8.0_71"
Java(TM) SE Runtime Environment (build 1.8.0_71-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.71-b15, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1) create two script files "classpath.js" and "classpath-test.js" (see "source code for executable test case" - test scripts with more abstraction failed to reproduce issue reliably enough)

2) start the jjs shell via: jjs -pcc=true -ot=true -doe=true
3) load classpath-test.js via JS statement: load('./classpath-test.js');
4) load classpath.js via JS statement: load('./classpath.js');
5) exit the jjs shell via: exit();

6) repeat steps 2 through 5 at least three times (it always requires three runs on my machine to reproduce the issue)

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
All repetitions of steps 2 through 5 produce the exact same output:

output of 3)
function (name, deps, factory){
        // simply call factory with the expected Java object
        factory(Java);
}

output of 4)
java.lang.RuntimeException: java.lang.ClassNotFoundException: de.axelfaust.alfresco.nashorn.repo.loaders.AlfrescoClasspathURLStreamHandler
java.lang.RuntimeException: java.lang.ClassNotFoundException: de.axelfaust.alfresco.nashorn.repo.loaders.AlfrescoClasspathURLStreamHandler
        at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:397)
 [... stack frames ommitted for readability ...]
        at jdk.nashorn.tools.Shell.main(Shell.java:111)
Caused by: java.lang.ClassNotFoundException: de.axelfaust.alfresco.nashorn.repo.loaders.AlfrescoClasspathURLStreamHandler
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
 [... stack frames ommitted for readability ...]
        at jdk.nashorn.internal.scripts.Script$Recompilation$7$846$classpath.classpath_loader_root$classpath_loader$streamHandler(./classpath.js:24)
        at jdk.nashorn.internal.scripts.Script$Recompilation$16$541A$classpath$cu1$restOf.classpath_loader_root$classpath_loader(./classpath.js:20)
        at jdk.nashorn.internal.scripts.Script$Recompilation$11$287AAA$classpath_test.define(./classpath-test.js:15)
        at jdk.nashorn.internal.scripts.Script$Recompilation$10$138$classpath.classpath_loader_root(./classpath.js:12)
        at jdk.nashorn.internal.scripts.Script$Recompilation$9$103$classpath.:program(./classpath.js:4)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:637)
        at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494)
        at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
        ... 13 more

This exception is EXPECTED as we have not included the custom Java class on the classpath.
ACTUAL -
the output of 4) changes on a repitition of steps 2 through 5 (in my environment it reliably occurs on the 3rd repetition)

java.lang.NullPointerException
jdk.nashorn.internal.runtime.ParserException: java.lang.NullPointerException
        at jdk.nashorn.internal.runtime.Context$ThrowErrorManager.error(Context.java:434)
        at jdk.nashorn.internal.parser.Parser.handleParseException(Parser.java:386)
        at jdk.nashorn.internal.parser.Parser.parse(Parser.java:285)
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.reparse(RecompilableScriptFunctionData.java:405)
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.compileTypeSpecialization(RecompilableScriptFunctionData.java:723)
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.getBest(RecompilableScriptFunctionData.java:905)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.getBest(ScriptFunctionData.java:375)
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.getReturnType(RecompilableScriptFunctionData.java:893)
        at jdk.nashorn.internal.codegen.TypeEvaluator.getEvaluatedType(TypeEvaluator.java:236)
        at jdk.nashorn.internal.codegen.TypeEvaluator.getOptimisticType(TypeEvaluator.java:95)
        at jdk.nashorn.internal.codegen.Compiler.getOptimisticType(Compiler.java:576)
        at jdk.nashorn.internal.codegen.OptimisticTypesCalculator.leaveOptimistic(OptimisticTypesCalculator.java:234)
        at jdk.nashorn.internal.codegen.OptimisticTypesCalculator.leaveDefault(OptimisticTypesCalculator.java:200)
        at jdk.nashorn.internal.ir.visitor.NodeVisitor.leaveCallNode(NodeVisitor.java:233)
 [... stack frames ommitted for readability ...]
        at jdk.nashorn.internal.codegen.CompilationPhase.transformFunction(CompilationPhase.java:628)
        at jdk.nashorn.internal.codegen.CompilationPhase.access$100(CompilationPhase.java:55)
        at jdk.nashorn.internal.codegen.CompilationPhase$OptimisticTypeAssignmentPhase.transform(CompilationPhase.java:255)
        at jdk.nashorn.internal.codegen.CompilationPhase.apply(CompilationPhase.java:624)
        at jdk.nashorn.internal.codegen.Compiler.compile(Compiler.java:655)
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.compileTypeSpecialization(RecompilableScriptFunctionData.java:725)
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.getBest(RecompilableScriptFunctionData.java:905)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.getBest(ScriptFunctionData.java:375)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.getBestInvoker(ScriptFunctionData.java:237)
        at jdk.nashorn.internal.runtime.ScriptFunction.findCallMethod(ScriptFunction.java:871)
        at jdk.nashorn.internal.runtime.ScriptObject.lookup(ScriptObject.java:1825)
        at jdk.nashorn.internal.runtime.linker.NashornLinker.getGuardedInvocation(NashornLinker.java:104)
        at jdk.nashorn.internal.runtime.linker.NashornLinker.getGuardedInvocation(NashornLinker.java:98)
        at jdk.internal.dynalink.support.CompositeTypeBasedGuardingDynamicLinker.getGuardedInvocation(CompositeTypeBasedGuardingDynamicLinker.java:176)
        at jdk.internal.dynalink.support.CompositeGuardingDynamicLinker.getGuardedInvocation(CompositeGuardingDynamicLinker.java:124)
        at jdk.internal.dynalink.support.LinkerServicesImpl.getGuardedInvocation(LinkerServicesImpl.java:154)
        at jdk.internal.dynalink.DynamicLinker.relink(DynamicLinker.java:253)
        at jdk.nashorn.internal.scripts.Script$Recompilation$9$287AAA$classpath_test.define(./classpath-test.js:15)
        at jdk.nashorn.internal.scripts.Script$Recompilation$8$138$classpath.classpath_loader_root(./classpath.js:12)
        at jdk.nashorn.internal.scripts.Script$Recompilation$7$103$classpath.:program(./classpath.js:4)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:637)
        at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494)
        at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
        at jdk.nashorn.internal.runtime.Context.evaluateSource(Context.java:1224)
        at jdk.nashorn.internal.runtime.Context.load(Context.java:837)
        at jdk.nashorn.internal.objects.Global.load(Global.java:1530)
        at jdk.nashorn.internal.scripts.Script$Recompilation$5$\^shell\_.:program(<shell>:1)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:637)
        at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494)
        at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
        at jdk.nashorn.internal.runtime.Context.eval(Context.java:736)
        at jdk.nashorn.internal.runtime.Context.eval(Context.java:671)
        at jdk.nashorn.tools.Shell.readEvalPrint(Shell.java:438)
        at jdk.nashorn.tools.Shell.run(Shell.java:160)
        at jdk.nashorn.tools.Shell.main(Shell.java:135)
        at jdk.nashorn.tools.Shell.main(Shell.java:111)
java.lang.NullPointerException
java.lang.NullPointerException
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.compileTypeSpecialization(RecompilableScriptFunctionData.java:728)
        at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.getBest(RecompilableScriptFunctionData.java:905)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.getBest(ScriptFunctionData.java:375)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.getBestInvoker(ScriptFunctionData.java:237)
        at jdk.nashorn.internal.runtime.ScriptFunction.findCallMethod(ScriptFunction.java:871)
        at jdk.nashorn.internal.runtime.ScriptObject.lookup(ScriptObject.java:1825)
        at jdk.nashorn.internal.runtime.linker.NashornLinker.getGuardedInvocation(NashornLinker.java:104)
        at jdk.nashorn.internal.runtime.linker.NashornLinker.getGuardedInvocation(NashornLinker.java:98)
        at jdk.internal.dynalink.support.CompositeTypeBasedGuardingDynamicLinker.getGuardedInvocation(CompositeTypeBasedGuardingDynamicLinker.java:176)
        at jdk.internal.dynalink.support.CompositeGuardingDynamicLinker.getGuardedInvocation(CompositeGuardingDynamicLinker.java:124)
        at jdk.internal.dynalink.support.LinkerServicesImpl.getGuardedInvocation(LinkerServicesImpl.java:154)
        at jdk.internal.dynalink.DynamicLinker.relink(DynamicLinker.java:253)
        at jdk.nashorn.internal.scripts.Script$Recompilation$9$287AAA$classpath_test.define(./classpath-test.js:15)
        at jdk.nashorn.internal.scripts.Script$Recompilation$8$138$classpath.classpath_loader_root(./classpath.js:12)
        at jdk.nashorn.internal.scripts.Script$Recompilation$7$103$classpath.:program(./classpath.js:4)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:637)
        at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494)
        at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
        at jdk.nashorn.internal.runtime.Context.evaluateSource(Context.java:1224)
        at jdk.nashorn.internal.runtime.Context.load(Context.java:837)
        at jdk.nashorn.internal.objects.Global.load(Global.java:1530)
        at jdk.nashorn.internal.scripts.Script$Recompilation$5$\^shell\_.:program(<shell>:1)
        at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:637)
        at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494)
        at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
        at jdk.nashorn.internal.runtime.Context.eval(Context.java:736)
        at jdk.nashorn.internal.runtime.Context.eval(Context.java:671)
        at jdk.nashorn.tools.Shell.readEvalPrint(Shell.java:438)
        at jdk.nashorn.tools.Shell.run(Shell.java:160)
        at jdk.nashorn.tools.Shell.main(Shell.java:135)
        at jdk.nashorn.tools.Shell.main(Shell.java:111)

REPRODUCIBILITY :
This bug can be reproduced often.

---------- BEGIN SOURCE ----------
=== Source of classpath-test.js
// these need to be globally defined
var applicationContext, getSimpleLogger, define;

applicationContext = null;
getSimpleLogger = function() {
return Object.create(Object.prototype, {
traceEnabled : {
value : false
}
});
};

define = function (name, deps, factory){
// simply call factory with the expected Java object
factory(Java);
};

=== Source of classpath.js (https://github.com/AFaust/alfresco-nashorn-script-engine/blob/cadf69c2e3fb91fa58c57b8b92dab6e435ca5c67/repository/src/main/resources/de/axelfaust/alfresco/nashorn/repo/loaders/classpath.js)
/* globals -require */
/* globals getSimpleLogger: false */
/* globals applicationContext: false */
(function classpath_loader_root()
{
    'use strict';
    // applicationContext only set during engine setup
    var streamHandler = applicationContext ? applicationContext.getBean('de.axelfaust.alfresco.nashorn.repo-classpathURLStreamHandler')
            : null;

    // non-extensible raw classpath loader (scripts located anywhere in classpath)
    define('classpath', [ 'nashorn!Java' ], function classpath_loader(Java)
    {
        var URL, logger, loader;

        logger = getSimpleLogger('de.axelfaust.alfresco.nashorn.repo.processor.NashornScriptProcessor.loader.classpath');
        URL = Java.type('java.net.URL');
        if (streamHandler === null)
        {
            streamHandler = (function()
            {
                var AlfrescoClasspathURLStreamHandler;

                AlfrescoClasspathURLStreamHandler = Java
                        .type('de.axelfaust.alfresco.nashorn.repo.loaders.AlfrescoClasspathURLStreamHandler');
                streamHandler = new AlfrescoClasspathURLStreamHandler();
                streamHandler.basePath = 'alfresco';
                streamHandler.extensionPath = 'extension';

                return streamHandler;
            }());
        }

        /**
         * This loader module provides the capability to load classpath-stored scripts as AMD modules.
         *
         * @exports classpath
         * @author Axel Faust
         */
        loader = {
            /**
             * Loads a script stored on the classpath from normalized module ID.
             *
             * @instance
             * @param {string}
             * normalizedId - the normalized ID of the module to load
             * @param {function}
             * require - the context-sensitive require function
             * @param {function}
             * load - the callback to load either a pre-built object as the module result or a script defining a module from a
             * script URL
             */
            load : function classpath_loader__load(normalizedId, require, load)
            {
                var url = new URL('rawclasspath', null, -1, normalizedId, streamHandler);

                if (logger.traceEnabled)
                {
                    logger.trace('Loading module id {} from classpath', normalizedId);
                }

                load(url, true);
            }
        };

        Object.freeze(loader.load);
        Object.freeze(loader);

        return loader;
    });

    // extensible alfresco classpath loader (scripts located in /alfresco/extension/ or /alfresco/)
    define('extensible-classpath', [ 'nashorn!Java' ], function extensible_classpath_loader__load(Java)
    {
        var URL, logger, loader;

        logger = getSimpleLogger('de.axelfaust.alfresco.nashorn.repo.processor.NashornScriptProcessor.loader.extensible-classpath');
        URL = Java.type('java.net.URL');
        if (streamHandler === null)
        {
            streamHandler = (function()
            {
                var AlfrescoClasspathURLStreamHandler;

                AlfrescoClasspathURLStreamHandler = Java
                        .type('de.axelfaust.alfresco.nashorn.repo.loaders.AlfrescoClasspathURLStreamHandler');
                streamHandler = new AlfrescoClasspathURLStreamHandler();
                streamHandler.basePath = 'alfresco';
                streamHandler.extensionPath = 'extension';

                return streamHandler;
            }());
        }

        /**
         * This loader module provides the capability to load "extensible classpath"-stored scripts as AMD modules in such a way that
         * scripts in the /alfresco/extension/ override scripts in /alfresco/.
         *
         * @exports extensible-classpath
         * @author Axel Faust
         */
        loader = {
            /**
             * Loads a script stored on the "extensible classpath" from normalized module ID.
             *
             * @instance
             * @param {string}
             * normalizedId - the normalized ID of the module to load
             * @param {function}
             * require - the context-sensitive require function
             * @param {function}
             * load - the callback to load either a pre-built object as the module result or a script defining a module from a
             * script URL
             */
            load : function extensible_classpath_loader__load(normalizedId, require, load)
            {
                var url = new URL('extclasspath', null, -1, normalizedId, streamHandler);

                if (logger.traceEnabled)
                {
                    logger.trace('Loading module id {} from extensible classpath', normalizedId);
                }

                load(url, true);
            }
        };

        Object.freeze(loader.load);
        Object.freeze(loader);

        return loader;
    });
}());

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Disabling either persistent code cache or optimistic types has in all tests shown to reliably work around this issue.