ADDITIONAL SYSTEM INFORMATION :
Windows 7 64-bit
Java Web Start 11.221.2.11 amd64
Using JRE version 1.8.0_221-b11 Java HotSpot(TM) 64-Bit Server VM


A DESCRIPTION OF THE PROBLEM :
Running a jnlp application from a trusted partner (connected to over private network), see launch file below. At some point the pac file is being parsed and an error occurs. PAC file is based around ZScaler proxy. Possibly when it wants to do a CRL lookup as there are https resources secured using a globalsign cert and I think this is where the error occurs.

If someone contacts me privately I will share the PAC file itself.
<?xml version="1.0" encoding="UTF-8"?>
<jnlp codebase="https://....../...../downloads/"
  spec="6.0" xmlns:jfx="http://javafx.com">
  <information>
    <title>.........</title>
    <vendor>..............</vendor>
    <homepage href="http://www......com/"/>
    <description>..............</description>
    <description kind="short">................</description>
    <icon href="../images/...._64.png"/>
    <shortcut online="true">
      <menu submenu=".................."/>
    </shortcut>
  </information>
  <security>
    <all-permissions/>
  </security>
  <resources arch="amd64" os="Linux">
    <property name="jnlp.packEnabled" value="true"/>
    <!-- Refer to the 32-bit and 64-bit maxHeapSize settings in web.xml -->
    <j2se initial-heap-size="64M"
      java-vm-args="-d64 -XX:+HeapDumpOnOutOfMemoryError"
      max-heap-size="64M" version="1.7+"/>
    <jfx:javafx-runtime
.................................
.....................................................
.............................................................................

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Do anything that will cause the PAC file to be parsed I assume. I can share the jnlp file if required, but I doubt it's relevant.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
App to parse PAC file and connect out to do CRL checks.
ACTUAL -
java.io.IOException: Unable to tunnel through proxy. Proxy returns "HTTP/1.0 502 Bad Gateway"
at sun.net.www.protocol.http.HttpURLConnection.doTunneling(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.access$200(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection$9.run(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection$9.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessController.doPrivilegedWithCombiner(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
at com.sun.deploy.net.HttpUtils.followRedirects(Unknown Source)
at com.sun.deploy.net.BasicHttpRequest.doRequest(Unknown Source)
at com.sun.deploy.net.BasicHttpRequest.doHeadRequestEX(Unknown Source)
at com.sun.deploy.cache.ResourceProviderImpl.checkUpdateAvailable(Unknown Source)
at com.sun.deploy.cache.ResourceProviderImpl.isUpdateAvailable(Unknown Source)
at com.sun.deploy.cache.ResourceProviderImpl.getResource(Unknown Source)
at com.sun.deploy.cache.ResourceProviderImpl.getResource(Unknown Source)
at com.sun.javaws.LaunchDownload$DownloadTask.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

CacheEntry[http://..../PAC/....pac]: updateAvailable=true,lastModified=Fri Aug 30 20:49:18 BST 2019,length=10710
javax.script.ScriptException: <eval>:156:5046 Expected ; but found if
 function alert() {} function FindProxyForURL(url, host) { Rest of PAC file not included

CUSTOMER SUBMITTED WORKAROUND :
Manually configure proxy settings in java control panel - not use the pac file in "use browser settings"

FREQUENCY : always