Nanite: unused VertexInterpolator node disables Opacity Mask (material renders opaque)

UE - Rendering - Architecture - Jun 8, 2026

On Nanite meshes, placing a VertexInterpolator node in a material graph without using it (unconnected, or routed through a disabled static switch) silently breaks the Opacity Mask and the material r ...

ApplicationReceivedScreenOrientationChangedNotificationDelegate does NOT work properly on Android

UE - Platform - Mobile - Aug 5, 2019

ApplicationReceivedScreenOrientationChangedNotificationDelegate supports iOS but not Android. Probably, Java_com_epicgames_ue4_GameActivity_nativeOnConfigurationChanged should be useful for fix thi ...

ensure(false) being fired in FGenericParticlePairMidPhase::FindOrCreateConstraint from key collision

UE - Runtime - Simulation - Jan 27, 2025

ensure(false) being fired in FGenericParticlePairMidPhase::FindOrCreateConstraint from key collision. The licensee reports one of their users reported this issue and they were able to reproduce a fe ...

Spot Light USD Export Produces Incorrect Intensity Values Based on Cone Angle and Source Radius

UE - Editor - Open File Formats - USD - Apr 3, 2026

UPDATE: Should be fixed as of CL#52537078 (fb7af1) USD: Bake all frames of exposure animation tracks. When exporting Unreal Engine spot lights from a level to USD, lights with identical EV intensit ...

Physics enabled Child Actor components that spawn with with a delay, always spawns at world origin

UE - Gameplay - Jun 3, 2016

Physics enabled Child Actor components that spawn with with a delay, always spawns at world origin **This is a regression. It was working in 4.11.2 Could also be related to: [Link Removed] User D ...

Inconsistent ListView entry sizes can prevent the ListView from being scrolled to the bottom

UE - AI Workflows - UI Systems - Slate - May 4, 2022

Since the contents of a ListView are virtualized, the ListView estimates the size of the scroll box's contents based on the on-screen elements. This can lead to some situations where DistanceFromBot ...

Composite font uses a sub-font, even when the sub-font doesn't support the character

Tools - Apr 7, 2016

I have a fix for this shelved in CL# 2937344, so it would be good to get it into 4.12 once the user verifies the fix. ...

MotionWarping does not recognize new MontageInstance with the same montage

UE - MVF Character - Animation - Jan 11, 2023

When the same AnimMonotage is played again while moving with MotionWarping & RootMotion, UAnimNotifyState_MotionWarping does not recognize it. From licensee: The issue was that in URootMotionMod ...

[CrashReport] Linux_PlatformCreateDummyGLWindow()

UE - Platform - Linux - Nov 16, 2017

This is a trending Linux crash in the 4.18 release Callstack from Log[2017.11.10-14.42.41:021][ 0]LogLinux: Error: appError called: Assertion failed: [File:/media/***/OS/UnrealEngine-release/Engi ...

AddComponent node fails to be scheduled after adding an "expose on spawn" variable to an ActorComponent-based Blueprint Class.

UE - Gameplay - Blueprint - Nov 13, 2015

If an existing AddComponent node is placed in an Actor Blueprint's Event Graph for a custom ActorComponent-based Blueprint Class, the node will fail to be scheduled after adding a variable marked "E ...