We have tasks that only cleanup in ExitState while using bShouldStateChangeOnReselect=false in FN. Looking over code, most places using that do utilize StateCompleted for cleanup, and we use both ExitState and StateCompleted for FMassUseSmartObjectTask.
Are you seeing this happening in the engine MoveTo task as well? I know we are reworking both MoveTo and RunEQS tasks to use the tickless pattern for 5.6, but I have not seen or heard any reports from our FN teams about leaks with the tasks.
-James