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Behavior Tree crash when adding Blackboard Decorator

Hi you all!

I'm using the awesome Behavior Tree editor and I've encountered an error that makes the UE4 Editor crash. This happens every time when I add a Blackboard decorator in a Selector Node and click on it to inspect values.

I've tried to replicate this in other projects (ShooterGame i.e.) and the Blackboard Decorator was added correctly.

Thanks in advance.

Product Version: Not Selected
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asked May 20 '14 at 11:51 AM in Bug Reports

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avatar image louislitt83 Sep 18 '18 at 08:09 AM

Hey, nice answer. Loved the thought behind it. Cheers!



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3 answers: sort voted first

Hi apuntoprieto,

I've found similar situation [version 4.1]. This occurs when you add decorator "Does Path Exists", then FBlackboardKeySelector::CacheSelectedKey method proceeds with SelectedKeyId == 255 even if bNoneIsAllowedValue is false. In this situation, SelectedKeyName is "SelfActor", which doesn't exist in blackboard keys collection :)

It's possible that having "SelfActor" in many cases is mandatory. Let's just wait for answer from Staff. Cheers!

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answered May 20 '14 at 01:13 PM

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avatar image apuntoprieto May 20 '14 at 03:28 PM

Yeah, mpo!

I've set the first key of my Blackboard to a SelfActor reference and it doesn't crash for now.

Thanks a lot!

avatar image Alexander Paschall ♦♦ EPIC Aug 26 '14 at 08:26 PM


We have looked into this and we believe that the changes made to Blackboard assets fixed the crash in 4.4. I was not able to reproduce it myself in 4.4, but please let me know if you can still reproduce the issue. If you can, please post your reproduction steps for the issue at it occurs in 4.4.

I am marking the work-around as the accepted answer for now, in case people on previous builds need the information.

Thank you,


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I have had this exact same issue.

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answered May 26 '14 at 06:30 AM

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avatar image PeterLNewton Aug 02 '14 at 12:32 AM

Not to bring up old news, but this crash still exist in 4.3. By making the SelfActor first in the list of Blackboard Keys, it allowed me to edit my Blackboard Decorators.

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This issue happens for me in 4.4, with a brand new BehaviourTree and BlackboardData. Even with the SelfActor key first in the list, which was already added by default when I created the BlackboardData.

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answered Aug 21 '14 at 09:10 AM

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avatar image Alexander Paschall ♦♦ EPIC Aug 26 '14 at 08:21 PM


Thank you for your report. I was attempting this in 4.4, but did not experience the same issue. We believe the crash that was originally reported here has been fixed at this point, so this may be a new crash. Could you post this as a new report in the crash reports section so that I can assign a technician to investigate? You can link it here too, so that people will find it if they experience the same problem.



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