Summary
Assertion failed: Instances.Num() < 65535
File:
Engine/Source/Runtime/MovieScene/Private/EntitySystem/MovieSceneInstanceRegistry.cpp
Line:
74
Crash occurs inside the MovieScene/UMG animation system.
What Type of Bug are you experiencing?
Audio
Steps to Reproduce
Open Unreal Engine 5.8 project.
Create a Widget Blueprint containing multiple Widget Animations.
Create a Blueprint (BP_GameIntroManager) responsible for creating the intro widget.
On BeginPlay:
Create Widget
Add to Viewport
Play Widget Animations
Continue testing/recompiling the widget and Blueprint.
Eventually the editor crashes with the above assertion.
Expected Result
Widget animations should play normally without exceeding internal MovieScene instance limits.
Observed Result
Assertion failed:
Instances.Num() < 65535
Affects Versions
5.8
Platform(s)
Windows
Video
OS:
Windows 11
CPU:
AMD Ryzen 7
GPU:
RTX 3050 Laptop GPU
RAM:
32 GB
For crash reports, include your callstack
Assertion failed: Instances.Num() < 65535
[File:D:\build++UE5\Sync\Engine\Source\Runtime\MovieScene\Private\EntitySystem\MovieSceneInstanceRegistry.cpp]
[Line: 74]
UnrealEditor_Core
UnrealEditor_MovieScene
UnrealEditor_UMG
UnrealEditor_UMG
…
UnrealEditor_Engine
UnrealEditor_UnrealEd
Reproducible
Happens consistently after repeated testing/playing or editing widget animations.
Additional Notes
The project uses:
Unreal Engine 5.8
Blueprint only
UMG Widget Animations
BP_GameIntroManager
WBP_GameIntro
Widget created using Create Widget → Add to Viewport
The crash appears related to MovieScene instance creation while using Widget Animations.
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e4d26350be364e9797792772508213c2
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4afe7273f4d1405a907fb8db854f60f7