FStateTreeExecutionContext::GetDebugInfoString() outputs wrong info and crashes when using linked state trees

UE - AI - Debugging - Apr 17, 2025

When using State Trees, the AI Debugger can be accessed during play to show information about their current execution state. If a behavior tree is currently in a state that references a linked tree, ...

Setting spline in Niagara Override Parameters corrupts system after closing level

UE - Niagara - Mar 19, 2019

The USplineComponent appears to be corrupted. It will pass the null check, but operations done on the data cause the engine to crash. (See the linked UDN for more details) ...

Fields with Maximum resolution are not affecting all leaves of a Geometry Collection

UE - Simulation - Physics - Destruction - Apr 25, 2025

Fields with Maximum resolution are not affecting all leaves of a Geometry Collection on 5.4 and onwards. When calling GetRelevantParticleHandles() a Maximum Resolution field does return all particl ...

EQS Overlap test no longer recognizes custom Collision Object Channel

UE - AI - Nov 12, 2019

Environment Queries Ignore tests for Custom Collision Object Overlaps. Note: The expected behavior seems to have worked in 4.21, After following the steps to reproduce, I can verify a successful de ...

Delta struct serialized fast arrays replicating new elements with no changelist

UE - Networking - Jun 14, 2021

There is a scenario where delta struct serialized fast arrays can replicate changes that introduce additional elements to the array, but without changelists containing the new data. This needs furt ...

Struct with a single unaltered element will remove the element from the struct on compile

UE - Gameplay - Blueprint - Oct 7, 2015

If used inside a UMG Blueprint, a struct that has only one element will remove the element from the struct after compiling the blueprint. If the element is edited or a second element is added then ...

Incorrect config property serialization for UStructs used as TMap keys or contained in a TSet with a single value. Diffs taken from default-value of each member type, instead of from default-value of the struct

UE - CoreTech - Nov 18, 2024

Consider a UStruct with some basic type members, each one with a default value specified in the struct. Also consider a TSet or TMap with that struct as keys, used inside a UObject as a UProperty an ...

~FStaticMesh() can crash with race condition

UE - Graphics Features - Mar 21, 2017

UDN user reported frequent crashes in FStaticMesh::~FStaticMesh() on DrawListLinks[i]->Remove(false); Crash went away after adding critical sections to FStaticMesh::LinkDrawList(), FStaticMesh::Unl ...

StaticMesh->RenderData->LODResources[0].IndexBuffer empty in Standalone games.

UE - Gameplay - Nov 14, 2014

GetArrayView is returning incorrect values in Standalone games. The correct values are returned when played in Editor. ...

Crash when toggling the SmartLinkEnabled state of a NavLinkProxy specifically in a packaged game targeting Debug/Development

UE - AI - Navigation - Jan 24, 2025

The licensee has reported, and I was able to reproduce, that specifically in package builds targeting Development configuration, trying to toggle the SmartLinkEnabled state of a NavLinkProxy will cr ...