The system tests in rt/tests/system are intended to be run with jfxrt.jar on the classpath. However, the classpath is wrong such that the locally build jfxrt.jar is not used. This means that the binary_stub is being used which may be out of date and will not correctly reflect any local changes that the developer has made.

The problem is that in the :systemTests:test task, a relative path was used to the build directory, which is relative to that project rather than the root project as it should have been.