Unreal Engine Issues

Ensure condition failed: bPlayingBackwards ? (CurrentPosition <= PreviousPosition) : (CurrentPosition >= PreviousPosition)

The problem is caused by the animation sequence playback position being set out of range from Sequencer. The call stack is :  UE4Editor-AnimGraphRuntime.dll!FAnimSequencerInstanceProxy::UpdateAnim ...

[CrashReport] Crash on FMaterialEditor::OnCanPromoteToParameter()

This is a common crash in the 4.16 release (affecting Windows and Mac). A log file is attached. Users have not provided descriptions so additional information is not currently available. Windows C ...

Adjusting slider in Blend Space Animation causes editor to Crash

UPDATE: Date: 2/5/2015 Likely an instance of the same crash: [Link Removed] CrashReporter Bugg (Crash List): [Link Removed] When updating a project from UE4.4.3 to UE4.5.1 editor crashes when adju ...

Xcode 26/16.4 Metal Toolchain generates metallib's that are not compatible with iOS 16

Below is the error output from FirstPerson template as a C++ project: {+}../../../FirstPerson58CPP/Content/firstperson58cpp_sf_metal_es3_1_ios-metal_es3_1_ios.0.metallib, 5881486 bytes!2025-09-23 1 ...

[CrashReport] Linux crash - FMonitoredProcess::Launch()

This is an infrequent Linux crash occurring in 4.17.1. Callstack from Log[2017.09.06-15.26.30:028][666]LogLinux: Error: appError called: Assertion failed: Assertion failed: [File:/home/***/.local/ ...

Ensure occurs when turning on Vector Fields Developer Flag

The editor crashes with an ensure in the output log when Vector Field flag is toggled on in the show options of the viewport. LogOutputDevice:Error: === Handled ensure: === LogOutputDevice:Error: E ...

[CrashReport] Crash CheckForWorldGCLeaks() - EditorDestroyWorld()

This is a somewhat common but longstanding Mac crash that has affected users since at least 4.13. Recently in 4.17.1, the crashes are all occurring in various ARKit projects User DescriptionsI add ...

HTML5 fails to compile on Mac/Windows - Shipping

HTML5 fails to compile on Mac when built for shipping in binary I did not see this when packaging for development yesterday Does not occur in 4.14.3 The error appears to be WebGL relatedError: Web ...

[CrashReport] Mac crash - UE4Editor-Slate.dylib!PrepassWindowAndChildren(TSharedRef<SWindow, (ESPMode)0>)

This Mac crash originally occurred in 4.15 around March 2017, then decreased in frequency during 4.16 and 4.17. It may be starting to trend again in 4.18. There is one record of this occurring in 4 ...

WP HLOD Crash on Small Cell Sizes