Unreal Engine Issues
Unreal Engine Issues
Non-reflected header files not recognized by UHT
UE - Foundation - Core - Jul 28, 2015A user adds 3 .h files though Visual studio where the first contains a struct, the 2nd includes the 1st, the 3rd includes the 2nd and tries to make a variable of the struct declared in the 1st. The ...
[CrashReport] Assertion failed: Array index out of bounds - GetPhysicsTriMeshData() [modelcomponent.cpp:688]
UE - Simulation - Physics - Oct 30, 2017This is a semi-common crash that has occurred since at least 4.17.1. The callstack is nearly identical to [Link Removed], which was fixed in 4.18.0, however the error message and source context are ...
Assertion failed: (Index >= 0) & (Index < ArrayNum) when importing large Alembic file
UE - Editor - Content Pipeline - Datasmith - Importer - May 3, 2022Regression testing done on //UE4/Release-4.27.2 CL-18427296 and this issue did occur. [Link Removed] [Link Removed] Below is snips of customers description and proposed workaround:Importing alembi ...
Launch on fails during staging with a SafeCopyFile Exception for MfMedia.uplugin
Tools - Jan 10, 2017Was able to repro this on machines with and without machines set up for Xbone testing. ...
Children of editor-only actors do not maintain correct transforms when placed inside level instances for PIE and cooked builds
UE - World Creation - Worldbuilding Tools - Level Instances - Oct 20, 2025We have found an issue where children of editor-only actors get wrong transforms in PIE and cooked builds when placed inside level instances. This affects both engine version 5.5 and 5.6. The issue ...
FileSystemDerivedDataBackend may output a corrupted access log
UE - Foundation - Core - Derived Data - May 20, 2021This problem is caused by the AccessLogWriter has not been flushed at the termination. The following workaround flushes the Writer.class FFileSystemDerivedDataBackend : public FDerivedDataBackendInt ...
Crash when trimming animation and then undoing action
UE - Anim - Runtime - May 30, 2023Repro rate: 3/3 times This is a regression as the issue does not occur in 5.1.1 ...
Machine ID is not being shown on the crashreporter website
UE - Foundation - Core - CrashReportClient - Jan 13, 2017This is a regression from 4.14.3 ...
Nanite Displacement Bounds Mismatch Causes Floating Terrain Artifacts on Landscape
UE - Rendering - Graphics Features - Nanite - Mar 19, 2026Summary When Nanite Tessellation (Nanite Displacement) is enabled on a Landscape in UE 5.7.3, scaling the Displacement value via Multiply nodes in the material graph causes floating terrain ghost a ...
Exception on missing file during GC in horde storage
UE - Foundation - Horde - Storage - May 7, 2025During GC, if a file was manually deleted (but the storage system is still track), GC can erroneously fail (and never remove the reference). This causes a backup in GC, putting the whole algorithm i ...