@rlkoshak Yes, I can imagine how challenging it is to tackle down such an issue. I tried the same more than once - sometimes successful - most of the times not.
@rossko57 I remember that I saw similar errors (e.g.
IllegalStateException in xtext rule engine when using getThingStatusInfo() inside a lambda and triggeringItem problem (concurrency?)). Currently I do not have an idea on that too.