Found on OptaPlanner example manners2009. Reproducer send to Mario.
Fixed by https://github.com/droolsjbpm/drools/commit/ec835d8ea
Mario Fusco <mario.fusco> updated the status of jira DROOLS-460 to Resolved
Cherry-picked to 6.0.x branch with https://github.com/droolsjbpm/drools/commit/0a80dc9d7
Verified in BRMS 6.0.2 ER2.