I’m getting this same crash. I don’t think its the bool value causing the problem. I believe this happens when you try to assign a StateTreePropertyRef and there is a uObject reference somewhere in the stack of variables. In my case, I had a previous task in the same state that had a uObject output ref, once I removed that task it worked. I’ve seen the same crash if you have a uObject as a parameter of the stateTree.
Also, I searched for info on this crash while writing my own, nearly identical, set of “Set Param Ref” tasks it seems like updating stateTree params is a common pain point.