Unable to use blueprints after changing data in struct

Development Programming & Scripting Blueprint
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1

So I know there are a lot of these floating around to do with struct issues and simply refreshing the struct or the nodes/blueprints associated with it after changing variables but my problem seems more extreme:

After modifying a variable in a struct I then shut down the engine (5.6.0) and the next day the engine cannot even open without crashing. The first fix was to remove the map loading in through the Engine.ini file to get a blank level, this allows me to open without crashing.

However the struct and blueprints using the struct cannot be opened, if I click on them they immediately crash the engine. I cannot rename them to try and force a refresh, I cannot right click > Update Redirector References, I even bought a plugin to refresh blueprints but all result in immediate freezing and crashing. Basically interacting with the struct or BP’s results in crash.

I looked through old backups and the problem is there too, it only seems to have decided it’s an issue now and all versions. have this problem.

Here is a sample of the crash log, I know it’s the struct causing issue but it’s being used in a major class in my game so I reeeealy don’t want to have to remake it all as that’s months of work

Am I cooked?

[2025.08.17-02.08.19:719][222]LogProperty: Error: FStructProperty::Serialize Loading: Property ‘StructProperty /Game/UI/BuildingWidget/WBP_BuildingButton.WBP_BuildingButton_C:ExecuteUbergraph_WBP_BuildingButton:K2Node_CustomEvent_BuildingData’. Unknown structure.
[2025.08.17-02.08.19:719][222]LogProperty: Error: FStructProperty::Serialize Loading: Property ‘StructProperty /Game/UI/BuildingWidget/WBP_BuildingButton.WBP_BuildingButton_C:ExecuteUbergraph_WBP_BuildingButton:CallFunc_Array_Get_Item’. Unknown structure.
[2025.08.17-02.08.20:008][222]LogProperty: Error: FStructProperty::Serialize Loading: Property ‘StructProperty /Game/Buildings/Shelter/BP_Building_Shelter.BP_Building_Shelter_C:ExecuteUbergraph_BP_Building_Shelter:CallFunc_Array_Get_Item’. Unknown structure.
[2025.08.17-02.08.20:214][222]LogClass: Warning: Struct Property Building Data has a struct type mismatch (tag STRUCT_REINST_S_BuildingData_19(/Engine/Transient) != prop FallbackStruct(/Script/CoreUObject)) in package: /Game/UI/BuildingWidget/WBP_BuildingButton. If that struct got renamed, add an entry to ActiveStructRedirects.
[2025.08.17-02.08.20:444][222]LogProperty: Error: FStructProperty::Serialize Loading: Property ‘StructProperty /Game/XP/AC_XPUnlock_MechGarage.AC_XPUnlock_MechGarage_C:ExecuteUbergraph_AC_XPUnlock_MechGarage:CallFunc_GetDataTableRowFromName_OutRow’. Unknown structure.

2

Hey

Looking at your error log, could it be that you have renamed the struct itself?
There is a hint in your error, add that new name to the ActiveStructRedirects. Maybe it could help?

You need to add them to the [CoreRedirects] section of your DefaultEngine.ini file, in your project’s Config directory.

Format for adding a redirect is:

+StructRedirects=(OldName="/Script/MyGame.OldStructName", NewName="/Script/MyGame.NewStructName")

But without knowing details of the issue and exact struct changes it is impossible to help you, I am afraid.

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3

Thanks for having a look, unfortunately the struct hasn’t been renamed ever since I first made it :confused:

4

Error is pointing a struct property. One of the elements that’s being used is no longer available or renamed. Try updating the struct itself.

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5

That’s the problem I cannot physically do anything with the struct, I can’t open it, I can’t delete it, I can’t swap out a reference to it, any kind of interaction just crashes Unreal.

6

That sucks. Never had that issue. Yet when I’m working with structs I have every file that references it open. As I make changes to the struct I save it, then compile every file. Errors are noted and corrected.

Another need to test is to run a PIE session before you close out. It’ll tell you what files are bad.

7

this happens all the time with BP structs unfortunately, the only way i know of is to delete the struct (in windows explorer not UE) or if you’re lucky and have a backup copy it over.

this will stop the crashes allowing you to fix your project but all struct reference will be broken, including data tables so maybe back those up first.

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8

Yeah I think the whole project is basically done for, I can’t open the Blueprints that contain the struct either, regardless of if it exists or has been deleted in explorer which basically just means redoing everything.

Thanks for all the suggestions though.

9

well if you do start over, you can probably copy most of your assets directly to save some work.

i’d recommend doing structs in c++ its easy to do with no prior experience, and switch to data assets where possible

if you do use BP structs create a setter/getter function library so any modifications to the struct happen in one place only

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10

How about restoring the structure from the Saved/Autosaves/Game folder? Maybe your old working structure is there?
If that’s not possible, but you remember what changes you need to make to get the structure back to the old version, try creating a new empty project and copying your structure there. In the new project, change the structure to get it back to the old version. Save it. Then replace the structure in the broken project with this new one. I don’t know if this will work, but I think it’s worth a try.

11

I eventually found the problem!
It felt so weird to me that even my backups and autosaves were now crashing with the same issue. The structs needing to be refreshed was a seperate problem that was simply there because due to a different problem they could not be resolved.

The real problem was I had decided to reinstall/verify 5.6.0 as it was feeling a little buggy, in doing so it reset my macro libraries where I had created additional Macros like ForLoopWithDelay and ForEachLoopWithDelay. With these missing I could not open the problem blueprints as it would immediately crash.

I found this out by copying blueprints over to a new project, there I could open them and actually see the blank MacroInstance nodes, just had to remake those macros and replace to get it working again :face_with_bags_under_eyes:

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