Crash in 4.11 (SceneComponent.cpp) : assertion failed : childcount on level streaming unload by world composition


I’m actually migrating my project from UE4.9 to 4.11.1 and i get a crash in playing mode when my character move away from the starting map (not persistent one) in my open world.

The crash report explain clearly it’s in the garbage collection process the crash occur and with several test i discover it occur when the world composition try to unload a map. I change the streaming distance to a very high amount for testing and the crash is gone but it’s not a solution.

My game is in full blueprint for now, no C++ at all and worked perfectly in 4.9.

The crash occur on line 837 of the SceneComponent.cpp file.

I know similar bug exist in 4.10 and 4.11 (UE-23366 and UE-25360) but no one seems to occur with level streaming on all the report i have read.

Thank you in advance for your help.


A couple of things:

  • First, take your 4.9 project and delete the Saved and Intermediate folders before attempting to convert the project.
  • If you are still getting the crash, please provide the logs from your project’s Saved->Logs folder
  • Also, please cause the crash again and provide your Machine ID from the Crash Reporter window and ensure to hit send on the report.
  • Finally, do you have any steps that we can use to reproduce this issue in a clean project?

Thank you for the recommandation, infortunatly the crash is always present after importing from a 4.9 without Saved and Intermediate folders.

Machine ID : E70C833E4EFCF5F917C909A7C8A0CED8

My project become huge and i can direct you on how to reproduce the crash, sorry. I will try to make an empty project to search this week-end.


It seems i identify the problem for good.

In my game, i use AI controlled Character stored on streamed level who cause the crash.

In 4.11 when you spawn a character who instanciate at runtime other actor (weapon & shield actor in my case) in a streamed level you absolutly need to specify the actor Owner in the function SpawnActor or the level will crash at unloading.

The commentary for the entry Owner in blueprint who say the field Owner can be left empty is false in 4.11 (true in 4.9) for this situation.

Thank you for identifying the issue. Do you have a test project that you can provide? I have attempted to create a setup that reproduces the crash, but I haven’t been able to do so, which leads me to believe there is some small step I am missing.

If you have a test project, please upload it to dropbox and provide a link. You can PM me the link to it on the forums:


Based on the PM you’ve sent, it seems that you have not been able to reproduce this issue. As a result, I am going to mark this topic resolved as I await further information from you or any other community members who are having the same issue. Feel free to reopen this topic with repro steps or a test project so that we can reproduce it on our end.

Have a great day