Cook failure after upgrading from 4.23 to 4.26.1

Hi everyone,

I recently started porting our project to 4.26.1 from 4.23, and each time we try to cook, we get a variation of the following error:

Trying to remove MovieSceneNodeGroupCollection None.TP_Sequenced_Boss_NailGun_SplinterRight_C:None.None.None.NodeGroupCollection from a hash bucket that is currently being iterated over which is not allowed and may lead to undefined behavior!

Has anyone seen this before, or does anyone have any ideas as to what could be causing this?


I am also experiencing issues with 4.26.1 in this regard. It selects a BP from my project and throws this exact error at me. The only way I have got around it was to delete the BP and recreate it all over again. Is anyone else familiar with this and has some insight to share?

We had the same error in our project (sometimes during cooking, somethins in the Gather_Text commandlet).

After diffing the UE5 code, I think this got fixed in CL18437695 (or in case you are using GIT) by Epic. It seems to not be anywhere in the 4.26 or even 4.27 branch.

But if you are compiling the engine from source, porting it back should be kindof easy enough (some functions got shuffled around, but are easy enough to find in the 4.26 branch… also, if you compile with VS2017, you need to fix some compile errors about auto-template-deduction…)