ADDITIONAL SYSTEM INFORMATION :
Linux phoenix-dev3 3.10.0-957.21.2.el7.x86_64 #1 SMP Tue Jun 4 11:22:23 PDT 2019 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
When we upgraded from 1.8.0_241 to 1.8.0_251 one of our tests that run quite a large XSL transformation stopped working. It fails with an exception:

19:31:01 FATAL ERROR: 'Not targeting 34301: nop[0](1), but null'
19:31:01 Test: Test class de.telekom.integration.ws.primaplus.outbound.processor.XSLParentRelationshipTest says: :Not targeting 34301: nop[0](1), but null
19:31:01
19:31:01 :Not targeting 34301: nop[0](1), but null
19:31:01 Running test: Test testTransform(de.telekom.integration.ws.primaplus.outbound.processor.XSLParentRelationshipTest)
19:31:01
19:31:01 de.telekom.integration.ws.primaplus.outbound.processor.XSLParentRelationshipTest > testTransform FAILED
19:31:01 java.lang.ExceptionInInitializerError
19:31:01
19:31:01 Caused by:
19:31:01 java.lang.RuntimeException: javax.xml.transform.TransformerConfigurationException: Not targeting 34301: nop[0](1), but null
19:31:01 at de.telekom.integration.ws.primaplus.outbound.processor.XSLParentRelationshipTest.<clinit>(XSLParentRelationshipTest.java:47)
19:31:01
19:31:01 Caused by:
19:31:01 javax.xml.transform.TransformerConfigurationException: Not targeting 34301: nop[0](1), but null
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl.newTemplates(TransformerFactoryImpl.java:988)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl.newTransformer(TransformerFactoryImpl.java:761)
19:31:01 at de.telekom.integration.ws.primaplus.outbound.processor.XSLParentRelationshipTest.<clinit>(XSLParentRelationshipTest.java:44)
19:31:01
19:31:01 Caused by:
19:31:01 com.sun.org.apache.bcel.internal.generic.ClassGenException: Not targeting 34301: nop[0](1), but null
19:31:01 at com.sun.org.apache.bcel.internal.generic.BranchInstruction.updateTarget(BranchInstruction.java:217)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator.outline(MethodGenerator.java:1738)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator.outlineChunks(MethodGenerator.java:1169)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator.getGeneratedMethods(MethodGenerator.java:1899)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator.addMethod(ClassGenerator.java:137)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.Mode.compileNamedTemplate(Mode.java:557)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.Mode.compileTemplates(Mode.java:566)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.Mode.compileApplyTemplates(Mode.java:825)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.Stylesheet.compileModes(Stylesheet.java:622)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.Stylesheet.translate(Stylesheet.java:735)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.XSLTC.compile(XSLTC.java:478)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.compiler.XSLTC.compile(XSLTC.java:553)
19:31:01 at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl.newTemplates(TransformerFactoryImpl.java:947)
19:31:01 ... 2 more

It was working at 1.8.0_241 but I cannot mark that

REGRESSION : Last worked in version 8

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run quite large (for us it is ~1200 lines of code) XSLT against an XML file.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The file is transformed according to the XSLT.
ACTUAL -
Transformation fails with an exception.

CUSTOMER SUBMITTED WORKAROUND :
For that case, we switched to Saxon.

FREQUENCY : always