When try to use a parallel Node and play the game the editor freeze.
Does the freeze ever go away? If you give it enough time it should eventually crash/close with some useful information. Also, I’d suggest looking at your BTT_ChangeSpeed task if there’s any possibility for infinite loops. Have you tried using that task outside of the parallel node?
–mieszko
I just ran into the same problem. In my case, the editor never recovers(after ~30 min). When I break all and look through the code it appears as though a failure occurs in UBTCompositeNode::FindChildToExecute(…), calls NotifyDecoratorsOnFailedActivation(…) which fires the error string as “Child execution forbidden by Blackboard” which, for some reason, appears to hang up in the string class.
It has something to do with the decorator though. erWilly, have you tried just making a simple decorator (or removing the one causing the issue) that always succeeds to see if it resolves the crash? For me it resolves the crash so I just need to figure out whether I’m casting something inappropriately or what.
Hi Mieszko,
the BTT_ChangeSpeed and the selector work fine outside of simple parallel, I have to use Ctrl+Alt+Del to take down the editor.
Thanks for reporting this bug. Before fix gets into release build, please use following workaround:
Avoid situation, when there isn’t any valid task in background branch of parallel node. In your case, move blackboard decorator from selector to ChangeSpeed task and add short wait task (0.1s) to selector (last child) to act as a failsafe.
this one just bit me as well…is it fixed in 4.7? 
Yes it is.