Unreal Engine Issues

Cook non-determinism when serializing UObject pointers pointing to garbage

There's a cook determinism issue in the way UObject unversioned serialization handles UObject pointers pointing to garbage. Depending on GC timing, it can either be skipped (as a property matching C ...

"Detaching from existing linker" error messages when running Fixup Redirectors commandlet

Heterogeneous Volume Actor causes ensures to trigger in Debug builds

When a heterogeneous volume actor is used with a volume material in a debug build, the following ensures are triggered: Ensure condition failed: UniformBufferValue || EnumHasAnyFlags(AutomaticallyBo ...

Slow editor/PIE loading of UWorldPartitionHLODSourceActorsFromCell

Loading UWorldPartitionHLODSourceActorsFromCell takes a lot of time in editor + PIE when it contains a lot of actors per UWorldPartitionHLODSourceActorsFromCell (between 2K and 2K actors). ...

Missing PSO Precaches in the engine

A licensee wanted to report some missing PSO Precaching they found, which they have fixed locally: 1. UCableComponent doesn't implement CollectPSOPrecacheData or call CheckPSOPrecachingAndBoostPri ...

Physics Mover: AI movement and collisions can cause sharp increase in velocity

A pawn using the physics mover and using AI movement can sometimes gain an ton of velocity quickly upon colliding with another physics object. It seems to fix it self and revert back to it's origina ...

Sub-world partitions do not properly handle partial editor loading as world partition standalone level instances' spatially loaded actors do not get loaded even when the Level Instance is force loaded or loaded in by region.

Context Level Instancing is a level-based workflow designed to improve and streamline the level editing experience. In a standalone Level Behavior, when the Level Instance Actor is loaded through it ...

AreaNavModifiers generated by SplineNavModifierComponent have the component-to-world transform incorrectly applied twice

USplineNavModifierComponent was made available in UE 5.4. It generates several FAreaNavModifier instances covering a region with a certain thickness around a USplineComponent, and worked correctly u ...

bIncludeComponentLocationIntoBounds breaks bounds calculations

Bounds generation when bIncludeComponentLocationIntoBounds is active is broken. Both the calculation of the local bounds and the world bounds are incorrect (see screenshot). When that flag is acti ...

Lumen Card Sharing is active on material with custom primitive data

The wrong emissive value may be used on Nanite objects with custom primitive data when Lumen card sharing is enabled. This issue can be mitigated with: r.LumenScene.SurfaceCache.AllowCardSharing 0 ...