RigVMRegistry : The registry is not locked for writing yet : ensure statement error during cook

UE - Anim - Rigging - Control Rig - Sep 2, 2025

I am seeing an cook failure at the very beginning. It goes away with a retry step via Horde. Please find attached call stack. I am able to consistently reproduce it by wiping all the DDC cache and ...

Negatively scaled box collisions render back faces in Player Collision debug view

UE - Simulation - Physics - Sep 1, 2025

The player collision debug visualization for negatively scaled boxes is rendering the back faces, not the front faces. The debug primitives are rendered via the dynamic mesh builder. FDynamicMeshBui ...

When ControlRig.EnableAnimNodePerformanceOptimizations is enabled, the default pose briefly appears after the Control Rig is reinitialized

UE - Anim - Rigging - Control Rig - Sep 1, 2025

Since UE5.6, ControlRig.EnableAnimNodePerformanceOptimizations is enabled by default, and this appears to be causing the issue. Specifically, when the control rig’s construction event is processed, ...

Crash when running "MAP REBUILD ALLVISIBLE" with hidden sublevels and then changing maps

UE - World Creation - Worldbuilding Tools - Sep 1, 2025

Running the MAP REBUILD ALLVISIBLE editor command when the current map contains hidden sublevels causes a crash upon changing maps. The issue seems to be related to hidden sublevels being cleared in ...

Hardware Lumen Surface Cache Artifacts on Nanite Geometry

UE - Graphics Features - Lumen - Sep 1, 2025

When using Hardware Lumen with Nanite-enabled meshes in UE 5.6+, black / dark surface cache artifacts appear that result in generally darker and unstable lighting. These artifacts are not immediatel ...

GeometryCollectionPhysicsProxy::FieldParameterUpdateCallback() not removing invalid Commands, leading to performance issues

UE - Simulation - Physics - Destruction - Aug 30, 2025

GeometryCollectionPhysicsProxy::FieldParameterUpdateCallback() not removing invalid Commands, leading to performance issues. The licensee has provided their analysis: We seem to have stumbled acro ...

Crash When Loading Cooked Material Assets in Editor Due to Shader Serialization

UE - Rendering Architecture - Shaders - Aug 27, 2025

In Unreal Engine 5.6+, the new shader serialization logic in FShaderMapResourceCode::Serialize does not correctly handle cooked assets that are loaded back into the editor (e.g., from a mounted .pak ...

UMG Retainer Box renders incorrect colors with Color Vision Deficiency enabled

UE - Editor - UI Systems - UMG - Aug 27, 2025

When using a Retainer Box in UMG with Color Vision Deficiency enabled, the content inside the Retainer Box is rendered with incorrect colors compared to the rest of the UI. This bug is present in UE ...

GAS: Double attributes not shown GameplayDebugger

UE - Gameplay - Gameplay Ability System - Aug 27, 2025

Context The Gameplay Ability System lets devs specify numerical attribute properties in UAttributeSet subclasses. Although the preferred attribute property type is FGameplayAttributeData, GAS has l ...