Translucent materials in the PostMotionBlur pass can cause a flickering viewport artefact when using TAA

UE - Rendering - Graphics Features - Feb 5, 2025

There appears to be a bug relating to rendering multiple windows that can trigger under unknown circumstances. It has been reported on rectangle lights in the forums and on PostMotionBlur materials ...

Properties not serialized when moving actor/component depending on unrelated specifiers

UE - Framework - Blueprint - Sep 25, 2023

When an actor is moved on the level editor viewport, it is reconstructed along with its components, which at first makes their properties reset to their default state. Thankfully, this does not happ ...

Set Members in Struct node doesn't work if the Struct is contained within an Array

UE - Gameplay - Blueprint - Dec 9, 2014

Set Members in Struct node doesn't work if the Struct is contained within an Array. ...

Assertion failed: (Index >= 0) & (Index < ArrayNum) when importing large Alembic file

UE - Editor - Content Pipeline - Datasmith - Importer - May 3, 2022

Regression testing done on //UE4/Release-4.27.2 CL-18427296 and this issue did occur. [Link Removed] [Link Removed] Below is snips of customers description and proposed workaround:Importing alembi ...

Async Physics incorrectly interpolates when multiple physics ticks pass

UE - Runtime - Simulation - May 28, 2024

If a user set the transform of a Body from the game thread and physics is running multiple async ticks perf game tick, the transforms might be being calculated incorrectly. ...

Asynchronous Image Loading from Disk Documentation leads to memory leak

Docs - Sep 18, 2019

The documentation example to create your own asynchronous image load from disk results in a memory leak that is noticeable using the task manager.  ...

Add Submix Effect Blueprint Does Not Have Any Effect

UE - Audio - Dec 11, 2020

Adding a second effect to the Submix Effect Chain on a Submix works as expected, but when trying to add a Submix Effect via Blueprint, there is no effect.  This also applies to "Add Master Submix Ef ...

A chaos vehicle that moves at very high speeds with CCD enabled on the vehicle sometimes has a collision response that is abnormal where the vehicle loses a significant amount of speed when colliding with dynamic objects configured as One Way Interaction

UE - Runtime - Character - Dec 16, 2025

Context: Continuous Collision Detection (CCD) is being used on a Chaos Vehicle to avoid tunneling issues with certain surfaces as it prevents any missed collisions between fast moving particles and ...

Crash when casting to owner from AnimGraph

OLD - Anim - Sep 6, 2016

Crash occurs when casting back to the pawn owner from the Anim Graph. In this case, it is being used for "Copy Pose from Mesh" Workaround: Cast to Owner from Event Graph, defining variable as the ...

Changing blueprint default values inside arrays only updates loaded child blueprints

UE - Core - Systems - Jul 30, 2020

The rules for delta serialization in UE4 are complicated, and the editor tries to hide them from you, which works 90% of the time but can lead to confusion and data loss in other situations. In the ...