Indeed, and thanks for the test case (haven't run it yet, but the issue seems obvious). I intend to look at this in a week's time. If you want to take a stab at it, probably the best solution would be to hand off this book-keeping to the o.a.c.scxml.SCInstance class which manages the state for every executor instance.
Setting fix version to next release (v0.7).
Please note that the "Affects Version/s" field should generally be set to the latest release (in this case, v0.6 – I've changed that here).