From where is my Java code executing?

Question

I've got a generic Java problem baked into a specific roadblock.

I am attempting to set up Flashback on my Win10 box, but am hitting this stack trace on the command ./startAdminServer.sh -port 1234 --stacktrace

java.lang.IllegalArgumentException: URI has an authority component
    at java.io.File.<init>(File.java:397)
    at org.gradle.internal.classloader.ClasspathUtil.getClasspathForClass(ClasspathUtil.java:68)
    at org.gradle.internal.installation.CurrentGradleInstallationLocator.findDistDir(CurrentGradleInstallationLocator.java:54)
    at org.gradle.internal.installation.CurrentGradleInstallationLocator.locateViaClass(CurrentGradleInstallationLocator.java:45)
    at org.gradle.internal.installation.CurrentGradleInstallationLocator.locateViaClassLoader(CurrentGradleInstallationLocator.java:41)
    at org.gradle.internal.installation.CurrentGradleInstallationLocator.locate(CurrentGradleInstallationLocator.java:31)
    at org.gradle.internal.installation.CurrentGradleInstallation.locate(CurrentGradleInstallation.java:46)
    at org.gradle.internal.installation.CurrentGradleInstallation.get(CurrentGradleInstallation.java:41)
    at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:45)
    at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:36)
    at org.gradle.launcher.daemon.bootstrap.GradleDaemon.main(GradleDaemon.java:22)

Multiple searches have led to a "Java/Gradle doesn't like UNC paths" type answer. My goal is to figure out which UNC path is being pulled back by this stack trace.

I've peeled apart the stack trace (yay open source), but it gets at something about Java I don't currently understand. Specifically in this file

CodeSource codeSource = targetClass.getProtectionDomain().getCodeSource();

Where getProtectionDomain() is part of a system-level Java construct.

How do I troubleshoot which path getProtectionDomain is returning?

• Is there a search order I am unaware of?
• Are there default env locations/variables under consideration? etc.

Considerations:

• I have cloned Flashback directly to C:\ (i.e. the .jar I invoke is on C:\)
• I have Java 1.7.0_25-b17 installed (build 23.21-b01, mixed mode, sharing)
• I don't know what else is relevant here.