UEFN project crashes on startup after checked-in .uasset import through File Explorer

General Issues and Bug Reporting
1

Summary

My UEFN project is currently bricked and crashes on startup every time.

This started after I imported 27 .uasset files directly into the project folder through Windows File Explorer, accepted the “trust authors” prompt in UEFN, checked in the revision through Lore, closed UEFN, and then attempted to reopen the project.

The only meaningful change in that checked-in revision was the imported assets:

  • 3 Scene Graph entities
  • 2 static meshes
  • 20 textures
  • 2 materials

Deleting the local project folder and resyncing fresh did not resolve the issue. I also attempted manual recovery through PowerShell using the Lore CLI and tried removing the imported assets from disk, but the project still does not open.

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

Unreal Revision Control

Steps to Reproduce

  1. Open a UEFN project using Lore / UEFN revision control.
  2. Copy a folder of .uasset files directly into the local project directory using Windows File Explorer.
  3. In UEFN, accept the prompt to trust the authors.
  4. Check in the imported assets through Lore.
  5. Close UEFN.
  6. Reopen the same project.
  7. Observe that the project crashes on startup.
  8. Delete the local project folder and resync the project fresh.
  9. Attempt to open the project again.

Expected Result

The project should reopen normally after the .uasset import and check-in.

If an imported asset is invalid, unsupported, or incompatible, UEFN should provide a recoverable validation error, allow the bad assets to be removed, or allow the project to open without loading the bad content.

A fresh delete/resync should restore a usable local project state or provide a clear supported recovery path.

Observed Result

The project crashes on startup every time.

Fortnite Crash Reporter appears with:
“An Unreal process has crashed: UE-FortniteGame”

The crash summary repeatedly references UnrealEditorFortnite / UnrealEditorFortnite_Engine_Win64_Shipping.

Deleting the local project folder and resyncing fresh does not fix the issue. Manual Lore CLI rollback attempts and manual removal of the freshly imported assets from disk have not restored access. The project is still inaccessible through UEFN.

Platform(s)

PC / Windows
UEFN
Lore / UEFN revision control

Additional Notes

This is a production blocker.

The issue appears tied to a checked-in asset import revision. Once the bad state was checked in, normal local deletion and resync did not recover the project.

Please escalate to the UEFN/Lore engineering or support team. I need a supported way to remove, bypass, or repair the bad checked-in asset revision without being able to open the project in UEFN.

Attached:

  • Crash Reporter screenshot
  • Incident report PDF
2

UEFN_Lore_Unresolved_Incident_Report_For_Epic.pdf (83.9 KB)

Attached is a PDF explaining it thoroughly

3

Update: this incident has now been resolved to an openable rescue state.

Honestly, i had Codex do a deep analysis.
Codex worked for a total of 45min with me at Extra High + 1.5x speed
It read tons of files and read things i didnt know existed…
After a few follow ups it managed to identify with me
Spent a solid 4 hours or so fixing this tonight.

I am in the project now!
Below is a recap, including a pdf

The project was recovered after all active project .verse files were renamed out of the compile path and generated local editor state was cleared. The logs did not prove that a single .uasset was binary-corrupt; the stronger signal is that the direct File Explorer asset import changed the generated asset-reflection / compiler state enough for existing Verse/reflection issues to become fatal during startup.

The startup crash was occurring inside the Verse compiler, including SemanticAnalyzer.cpp Line 9320, Attributable.cpp Line 303

Important caveat: the project opens now, but this is not the final repair because all Verse gameplay code is temporarily disabled. I’m attaching a resolved recovery summary PDF with the exact recovery state, likely root cause class, and next steps.

UEFN_Lore_Resolved_Recovery_Update_For_Epic(1).pdf (64.8 KB)

4

Hi @Breast

You could do this some of the time in UE5, but you cannot use this method on UE6-main which is Effectively the new UEFN.

The correct function is to use the Migrate function

Epic Developers assistant says this

==============================================

To migrate assets from standard Unreal Engine to Unreal Editor for Fortnite (UEFN), use the built-in Content Browser. Right-click your desired assets, select Asset Actions > Migrate, verify the dependency list, and select your UEFN project’s Content folder as the destination. [1, 2, 3]

The destination UEFN project and the Unreal Engine source project both need to be running on UEFN/Unreal Engine 5.1 or later for the migration to work. [1]

Keep these guidelines in mind:

  • Supported Assets: UEFN doesn’t support all standard Unreal Engine asset types. Supported assets must comply with Fortnite’s performance requirements.
  • Templates: You can also use the Migrate tool to move assets directly from UEFN feature templates into your own active projects. [1, 2]

For full step-by-step instructions and a list of unsupported formats, you can check out the official Migrating Assets in UEFN and Unreal Engine guide.

Migrating Assets from Unreal Engine to Unreal Editor for Fortnite | Fortnite Documentation | Epic Developer Community

the new Lori only works with assets which conform to the above procedure as it needs to be UE6 compatible and checks the headers for correct Migration values

Thanks

PS you need to vote this up to get any response from Epic Support

5

Cheers man.
Very informative, thank you