Created attachment 881266 [details] maven reproducer
Created attachment 881267 [details] non maven reproducer
I have reproduced this with BRMS 6.0.1 CR2 #2, working on a more isolated reproducer.
*** Bug 1082988 has been marked as a duplicate of this bug. ***
Fixed by https://github.com/droolsjbpm/drools/commit/14cae3411
Cherry-picked to 6.0.x branch with https://github.com/droolsjbpm/drools/commit/37d0c2d03
Verified in BRMS 6.0.2 ER2.