The test does not work as reproducer - when I copy test-code only on top of commit 96f3f16de04cf9f460e07c6cfa982d340f1c3fa4 (the last commit before this PR in jdg-6.3.x history), the test is passing anyway.
I was not able to reproduce this bug reliably and given the probabilistic nature of this bug (and its fix, which is not an ultimate one), I'll close this bug.