UMG is crashing frequently

General Issues and Bug Reporting
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1

Summary

My UMG is crashing frequently. I’m not exactly sure how it happens, but I have several WBP files nested inside a single WBP, along with various variables, custom materials, and binds within each of them. I’m constantly saving and recompiling after every change I make, and it crashes randomly. These are the last few lines of my log. I looked for something similar in the forums, I’m not sure if it’s been reported yet.

Please select what you are reporting on:

Creative

What Type of Bug are you experiencing?

UI/Tools

Steps to Reproduce

Create multiple WBP files with variables, set up binds and custom materials, and save and compile after each step

Expected Result

Continue working without interruption

Observed Result

[2026.05.09-22.46.21:523][119]LogSourceControl: Backed up 1 file(s) on personal branch.
[2026.05.09-22.46.21:925][147]LogBlueprint: Compiling Blueprint ‘/Project/GameWBP/InventoryHUD/WBP_Main_Inventory_Slot.WBP_Main_Inventory_Slot’
[2026.05.09-22.46.22:193][147]LogGarbage: Collecting garbage
[2026.05.09-22.46.22:248][147]LogGarbage: GC Reachability Analysis total time: 55.35 ms (55.35 ms on reference traversal)
[2026.05.09-22.46.22:248][147]LogGarbage: 55.35 ms for GC - 0 refs/ms while processing 0 references from 0 objects with 0 clusters
[2026.05.09-22.46.22:248][147]LogGarbage: Freed 69440b from 14 GC contexts
[2026.05.09-22.46.22:248][147]LogGarbage: 0.633899 ms for Gather Unreachable Objects (2536 objects collected / 539292 scanned with 14 thread(s))
[2026.05.09-22.46.22:254][147]LogGarbage: 1.712002 ms for unhashing unreachable objects (2536 objects unhashed)
[2026.05.09-22.46.22:272][147]LogGarbage: GC purged 2536 objects (496823 → 494287) in 19.046ms (1 iteration(s))
[2026.05.09-22.46.22:276][147]LogUObjectHash: Compacting FUObjectHashTables data took 3.75ms

Platform(s)

PC

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umg_crash.png
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2

I’ve identified the exact cause of this crash. The issue is tied to a naming conflict during the duplication process in UMG. It occurs specifically when an element has been manually renamed using spaces and is then duplicated or pasted.

The editor fails to resolve the unique ID when spaces are present, triggering the “pure virtual function being called” error. Interestingly, the crash only triggers once you click on another element or lose focus on the duplicated one. If you rename the duplicate immediately before clicking away, the crash can be avoided.

Steps to reproduce:

  1. Create any UI element in UMG.
  2. Manually rename it and include a space in the name (e.g., “Main Menu”).
  3. Duplicate or Copy-Paste that element.
  4. Click on any other element in the hierarchy.
  5. The editor will crash.
2 Likes
3

Thanks! That happens to me a lot, I’ll take your workaround. :folded_hands:

8

FORT-1100507 is ‘Closed’ as ‘Fixed’. The issue will be addressed in 41.00.