Blueprint actors can not be casted until they have been opened after migration or being upgraded to a more recent engine version

UE - Framework - Blueprint - Jan 5, 2023

This is not a regression tested in //UE5/Release-5.0 CL20979098 After migrating an asset from an older engine version or upgrading a project to newer version Blueprints carried over can not be cast ...

Crash in AWorldDataLayers::InitializeDataLayerRuntimeStates() when quickly unloading then loading a sub-world partition

UE - World Creation - Worldbuilding Tools - Data Layers - Mar 6, 2025

From licensee: Since we integrated 5.5, we are experiencing a crash in AWorldDataLayers::InitializeDataLayerRuntimeStates() on this line check(ActiveDataLayerNames.IsEmpty() && LoadedDataLayerN ...

GenerateKDopAsSimpleCollision() clamps vertices that are close to the origin which results in inaccurate primitives

UE - Gameplay - Nov 10, 2015

When DOP simplified collision is generated for a mesh that has vertices that are close to the origin, part of the function till clamp any values between -0.5 and 0.5 to be 0.5 which will cause the r ...

Crash when adding Actor Components to a Spawnable Actor in Sequencer while it is despawned

UE - Anim - Sequencer - Feb 26, 2026

After migrating our project from UE 5.5 to 5.7, we are experiencing a consistent engine crash in the Sequencer. The crash occurs specifically when a user attempts to add a component to a Spawnable A ...

Linux Native Toolchain depends on libninfo5 which is not bundled

UE - Platform - Linux - Sep 6, 2019

libtinfo.so.5 => /lib/x86_64-linux-gnu/libtinfo.so.5 (0x00007fc27cf4d000) bschaefer@bschaefer-Precision-T7600:bin$ ldd ./clang linux-vdso.so.1 => (0x00007ffceefe3000) libpthread.so.0 => /lib/ ...

Changing the ComponentClass of a ACharacter twice and trying to set a SkeletalMeshAsset crashes the engine

UE - Anim - Jan 22, 2026

Changing the ComponentClass of a ACharacter twice and trying to set a SkeletalMeshAsset crashes the engine with a "Cannot replace existing object of a different class" message. The conditions to re ...

Merge Actors (Simplify) is broken with Substrate Shader Models Node

UE - Graphics Features - Substrate - Sep 29, 2025

Substrate Materials cannot be baked when Meshes are merged using the "Simplify" method. All textures except for the normal are reduced to a single black parameter. The normal texture produced does n ...

Enabling Strip Source Data On Cook on Geometry Collection is also stripping the Anchor flag of cooked assets

UE - Simulation - Core - Jul 20, 2025

Enabling Strip Source Data On Cook on Geometry Collection (GC) is also stripping the Anchor flag of cooked assets. The licensee has reported that once they do a build the Anchors disappear and GCs t ...

FString.Mid doesn't react appropriately when given negative values for the Count variable

UE - Foundation - Core - Jul 16, 2015

If you use a 5 character string (hello) to call the Mid function and provide 0 for start, -1 for count, it'll give you the entire string. This should either return an assert or treat all negatives a ...