At least 1 module failed remote validation

General Issues and Bug Reporting
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Summary

Here’s the ready-to-paste Epic support ticket content:

Subject: UEFN Remote Validation Failure — “At least 1 module failed remote validation” — Backend Cache Reset Required

Description:

We are experiencing a critical blocking issue on our UEFN project that prevents us from generating a Private Version Code or launching a session. We believe this requires a server-side / backend cache reset on Epic’s end, as all local remediation steps have been exhausted.

Error:
At least 1 module failed remote validation

Log detail:
Supplied candidate api does not match expected public api

Missing assets flagged in logs:

  • EngineMaterials/Good64x64TilingNoiseHighFreq
  • EngineMaterials/WorldGridMaterial_2
  • EngineMaterials/DefaultDiffuse_2

Affected Islands:

  • FFW Experience — 3527-6691-0764
  • Esperienza Neve — 8407-4348-1757

(Confirm which island code to lead with based on which is actively affected)

Timeline:
The issue began immediately following a Fortnite engine update in early April 2026. A warning about an incoming update appeared during a push. Even after rolling back that push, the error persisted across all subsequent attempts.

Scope of Impact:

  • Affects multiple machines (2 confirmed)
  • Affects multiple accounts
  • Affects fresh installs of the project on a separate machine
  • Does not affect other UEFN projects on the same machines — a Programming Test Project validates and runs normally

Troubleshooting Already Completed:

  • Cleared project cache (both machines)
  • Validated the Unreal project
  • Updated redirector references
  • Left and rejoined the Fortnite team
  • Duplicated the project
  • Full fresh install on a separate machine
  • Rolled back through multiple previous pushes, including versions from early March 2026 (approx. one month prior)
  • Tested with a different Epic account

None of these actions resolved the issue.

Assessment:
Based on the evidence, this is not a local machine or project file issue. The missing engine materials are engine-level assets that appear to have changed during the recent Fortnite update, causing a validation mismatch between our project’s cloud record and the current UEFN runtime state.

We are requesting a manual backend/cloud cache reset for the affected island(s) to restore validation consistency. This resolution has been applied by Epic support in similar reported cases following engine updates.

Studio: Gravitaslabs

That’s everything Epic support needs to act on it. The key phrase is in bold — “manual backend/cloud cache reset” — make sure that stays in verbatim. Without it support will send back the standard local troubleshooting checklist.

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

Other

Steps to Reproduce

we are getting it specifically after the 40.0 update where we are not able to push for validation to create test code

Expected Result

not being able to validate

Observed Result

no test code, vlidation error

Platform(s)

Fortnite - unreal editor fortnite with the latest update of fortnite - 40.0