Crash when adding Actor Components to a Spawnable Actor in Sequencer while it is despawned (UE 5.7)

Development Character & Animation
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1

[Description]

After migrating our project from UE 5.5 to 5.7, we are experiencing a consistent engine crash in the Sequencer. The crash occurs specifically when a user attempts to add a component to a Spawnable Actor while its “Spawned” track is set to False.

[Reproduction Steps]

  1. Open or create a Level Sequence.
  2. Add an Actor and convert it to a Spawnable.
  3. Move the playhead to a frame where the Spawned track is set to False.
  4. In the Sequencer Outliner, right-click the Actor node and try to add any Component.
  5. Result: The engine crashes immediately.

[Technical Analysis]

The crash is triggered during selection synchronization. In FSequencer::SynchronizeExternalSelectionWithSequencerSelection(), the code attempts to access the Level of the bound object without verifying its validity.

When the actor is despawned, Actor->GetLevel() returns nullptr, causing an access violation in FLevelUtils::IsLevelLocked().

[Suggested Temporary Fix]

We have mitigated the crash by adding null checks for the Level pointer in Sequencer.cpp:

ULevel* ActorLevel = Actor->GetLevel();

if (ActorLevel && !FLevelUtils::IsLevelLocked(ActorLevel))

{

SelectedSequencerActors.Add(Actor);

}

[Requests]

  1. Is this a known regression in the 5.7 branch?
  2. Could you provide guidance on a more fundamental fix or confirm if a hotfix is planned?

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2

Hey there,

Thanks for raising this. It is a new bug. https://issues.unrealengine.com/issue/UE-367713

I’m discussing an alternative to your approach because while it will prevent the crash, it creates some bad data in the sequence. A better approach will need some investigation, as we’re unsure if the UI should allow you to do that or if it should, and what it would take to address it.

Dustin

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3

We do not have an expected timeline at the moment. I would follow the issue above to get an update on its status.

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4

Thanks.

The fix I applied was just a temporary workaround, not a formal proposal for the solution. I’ll be checking in occasionally to see if it’s been patched. Do you have an expected timeline or a specific month in mind for the fix?

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5

Yes, thank you.​

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