herve1234
May 21, 2026, 10:22am
1
Hi, I’m getting a few errors during the packaging process. I’ve managed to fix some of them, but there are a few I don’t understand. If anyone can help me out, that would be great.
LogProperty: Error: FStructProperty::Serialize Loading: Property ‘StructProperty /Game/FlexibleCombatSystem/Blueprints/AI/AI-Spawners/I_SpawnMarker.I_SpawnMarker_C:Pass AI Setup Data:AI Spawner Data’. Unknown structure.
Hello there @herve1234 !
Thanks for the log, I think the first entry is already quite critical:
PackagingResults: Error: FStructProperty::Serialize Loading: Property ‘StructProperty /Game/FlexibleCombatSystem/Blueprints/AI/AI-Spawners/I_SpawnMarker.I_SpawnMarker_C:Pass AI Setup Data:AI Spawner Data’. Unknown structure.
This means UE is not being able to find references for AI Spawner, either due missing/corrupted data, or the Struct itself not being properly read. It’s aiming particularly at I_SpawnMarker from the Flexible Combat System. So, let’s take a few steps to resolve the problem:
First of all, please make sure that the Flexible Combat System plugin is enabled in your project
Look for the element tied to AI Spawner Data, open it, and try recompiling it
Then, use the reference viewer to find it’s associated blueprints, and for each one of them, apply the “Refresh All Nodes” option, then save
You can also test with re-creating the affected variable, by removing and re-adding AI Spawner Data, then compile/save again
Next, in the content browser, look for your main Content folder, right click on it, and select “Fix Up Redirectors”
Finally, close your project, and clear it’s cache, via navigating to it’s main directory, and deleting folders Intermediate, Saved, and DerivedDataCache. Once completed, reopen UE, and test packaging again.
This should resolve the “Unknown structure” conflict. There’s another error in the log, an assertion failure tied to PCG, but it’s most likely a consequence of the first issue. Yet, if the problem persists, please send us an updated log, to investigate further.
Hope this helps, and good luck!
Ram07
May 21, 2026, 5:58pm
3
Hi, open those files where it says structure, and just recompile once or refresh node once on it and compile, save. do for both of those struct variables that are shown in log and then, it should cook fine.
Hello, thank you very much
PackagingResults: Error: RegisterComponentWithWorld: (/Game/Game/Map/Island.Island:PersistentLevel.Landscape_0.RootComponent0) Trying to register component in invalid or cleaned up world. Aborting.
Hey,
I think I’ve found the issue – it’s the level streams that were set to ‘Always Loaded’. I tested it with all levels set to ‘BP only’ and was able to package the project. The question is: is it possible to package the project with a level stream set to ‘Always Loaded’? I’m continuing to run tests to make sure that’s really the cause. All the best
Ram07
May 24, 2026, 5:14pm
6
can you create new level (blank level) - make it as starter map in project settings for default game map - package now and see if errors are coming?
Hey, Sorry for the late reply. I followed your instructions, but unfortunately there are some errors. What’s driving me crazy is that I didn’t have these “NiceInteractionSystem” errors before!
LogProperty: Error: FStructProperty::Serialize Loading: Property ‘StructProperty /Game/NiceInteractionSystem/UI/WB_InteractionStyle_Flat.WB_InteractionStyle_Flat_C:Update_UI_InteractionInfo:Info’. Unknown structure.
Ram07
May 28, 2026, 9:30am
8
can you go to those blueprints mentioned in logs and see if there are errors? if there are not, you can just right click on those struct variables and refresh and if you do for few and try to build again, you should not see them now in logs
That didn’t work; I also deleted the Saved/Intermediate/DerivedDataCache folders.
Is it because the NiceInteraction elements aren’t in the persistent level? They’re in a level stream.
Ram07
May 28, 2026, 5:14pm
10
very strange. is that plugin free? if yes, I can put in new project and package and see if i am getting errors. usually with struct, sometimes packaging error comes but when we refresh, next time, errors will not come - happened for me before.
also, you said, you will ask plugin developer, any response for it?
herve1234
May 28, 2026, 6:17pm
11
There we go, I’ve finally managed it, It took ages…
Ram07
May 28, 2026, 6:29pm
12
Haha great. It doesn’t happen every-time like this though - struct related errors.
Ram07
May 29, 2026, 8:45am
13
please keep this as resolved, thanks
I removed the BP AI Spawers and folders, but other errors have popped up.