The issue was that on windows. a scheduleImpl.schedule(Runnable, delay, MILLISECONDS) could finish earlier than expected.
I added a workaround to the scheduler, with this following trace:
calling another scheduler now as deliverTime " + deliveryTime + " < now=" + now
which is happening quite a lot on the windows box that was failing.
The test was replicated in loop and after this fix we couldn't make it fail again
Thanks for the hard work on this one!