Need help with crash log after level streaming messed with actors : Array Index Out of Bounds: -302333536 into an array of size 31

Development Programming & Scripting
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Some context because I took very few steps before my project crashes on play.

I introduced a new sub-level for level streaming and assigned a room of actors to that new sub level. Strangely, it asked me if I wanted to delete some grouped actors , but I cancelled the delete request and it worked. However my main level would no longer save, it told me I had illegal references to private objects. All of these were grouped actors, so I ungrouped them and resolved them one at a time.

Then it told me: I had an illegal reference to the sub-level, which was referenced by ‘LevelStreamingDynamic_0’ (at ‘/Game/CSConceptLevel.CSConceptLevel’) in its ‘LoadedLevel’ property (private object belongs to an external map).

The only way I solved this was to return everything to the persistent level and delete the sub level.

Finally I could save my main level again, but now that map (and only that map) crashes on play.

Here is the crash log text file. I only work with blueprint. There are a lot of errors I don’t care about right now, namely a bunch of missing files from an old plugin I’ve half way ripped out and left half of for reference. These are not new.

At the literal bottom of the text file it says what I think is most relevant:

2025.10.24-04.19.30:614][ 7]LogOutputDevice: Warning:

Script Stack (0 frames) :

[2025.10.24-04.19.30:617][ 7]LogWindows: Error: appError called: Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 783]

Array index out of bounds: -302333536 into an array of size 31

[2025.10.24-04.19.30:617][ 7]LogWindows: Windows GetLastError: The operation completed successfully. (0)

The last important context is that when I copy the level and delete ALL of the actors that could have been potentially “corrupted” by whatever problem the editor had with groups and sub levels, I am able to play as usual. So if I have to I will systematically delete each actor to find out what is causing this wild array index out of bounds issue.

Please let me know if anyone has insight into this and I would be very grateful.

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Hello there @TheDrownedForest!

I think you are in the right path, the main error in your log is definitely the out of bounds array, which means that one of your actors is keeping an invalid reference after being moved between levels. Grouping actors, moving them between levels, and then deleting or reloading said level can create corruption in your BPs.

That illegal reference you are seeing should point out which actor is responsible for the crash. Strangely, I was not able to find that entry in your provided crash log, could there be another log you are referring to?

Still, the approach you are taking is the correct one. I would make a duplicate of your project, start deleting actors, and test play, until the cultrip is isolated. Once you find it, you can try to fix it’s components, or replace it. After that, fix up your redirectors, close UE, and perform a cache clear of your project (open your main directory and delete folders Saved and Intermediate). Once rebuilt, test again, hopefully the issue should be fixed.