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. ...

Memory Leak occurring when switching between levels in Standalone

UE - Foundation - Core - Oct 29, 2015

A memory leak seems to occur when switching between levels multiple times. This is being monitored by memreport full ...

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 ...

Duplicating a blueprint that implements an interface and then removing that interface will cause compile errors that don't occur if the interface was removed from the original BP

UE - Gameplay - Blueprint Editor - Aug 1, 2020

See steps to reproduce. Looks like the fixup when saying Yes to "Would you like to transfer the interface functions to be part of your blueprint" doesn't work correctly on the duplicated BP. Inter ...

[MetaSounds][Stereo Mixer] - When changing the gain on the Right channel dynamically, the output has clicks and pops

UE - Audio - MetaSounds - Mar 31, 2022

When changing the right channel gain of the stereo mixer at runtime, it generates clicks and pops in the output. ...

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. ...

High Virtual Texture Sample/Lookup Cost when using a Virtual Texture in a Material Layer Blend

UE - Rendering Architecture - Materials - Mar 14, 2025

Some Material Attribute blends in Material Layer Blends can cause Virtual Texture samples to be duplicated in HLSL. This can be avoided by sampling the Virtual Texture in the Parent Material, and pa ...

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 ...