Adding a UMG widget to the viewport twice results in a crash.

UE - Editor - UI Systems - Sep 8, 2015

Attempting to add the same widget to the viewport twice will result in an assertion and crash. ...

tvOS crash on startup with Shared Material Shader Code enabled

UE - Platform - Mobile - Jul 9, 2019

Enabling Shared Material Shader Code will cause a crash on tvOS From user: "We originally enabled Share Material Shader Code long before trying a tvOS build, making this crash tricky to debug. W ...

Child actor passes a string to it's parent's overloaded constructor the incorrect string is received

UE - Gameplay - Sep 24, 2019

When a child actor passes a string to it's parent's overloaded constructor using an overridden function that returns a string it won't receive the correct string. I have verified that the correct fu ...

[AI] Using a Reference Value for scoring in an EQS test produces the opposite effect of its tooltip.

UE - AI - EQS - Sep 23, 2022

An EQS Query scores the tests using reference values opposite of how the comments and tooltips describe. It will score items closest to the referenced value lower than those further away, but the ex ...

Masked TwoSided material causing lumen direct lighting to leak through walls

UE - Graphics Features - Lumen - Apr 23, 2024

It appears that LumenScene's Hardware Ray Tracing is causing light leaking into a sealed room (which should be perfectly black). This bug does not appear to happen on AMD GPUs. ...

Packed level actors and Level instances are sometimes not included in HLOD build on a World Partition Level

UE - World Creation - Worldbuilding Tools - HLOD - Mar 14, 2025

Context World Partition - Hierarchical Level of Detail (HLOD) system uses custom HLOD Layers to organize large amounts of Static Mesh Actors and generate a single proxy mesh and Material. Problem T ...

Building Lighting will Generate Additional Lightmaps after Rotating Lightsource

UE - Graphics Features - Jul 7, 2015

Lightmap sizes seem inconsistent after rotating a light source and rebuilding the lighting. This causes concern about file sizes when packaging the project that is using baked static lighting. The ...

Orthographic Camera view doesn't work with movable directional light shadows and partly with stationary shadows

UE - Graphics Features - Feb 26, 2015

See attached video for clear examples. When using the orthographic camera perspective with default light settings to stationary for directional light source. Other light sources work as intended. T ...

Illegal Else Without Matching If

UE - Simulation - Physics - Feb 3, 2017

Looks like there's a missing if/else pair in BodyInstance.cpp ...

First Person Example Project Crash when character movement component is cast in viewport.

Tools - Jul 23, 2019

Crash is caused by incorrect cast to display ActorComponent in viewport (gizmo used to move it should not be present) ...