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Crash while unhiding streaming level in multiplayer

I've already posted this issue a few months ago: we were supposing to had found a solution but the problem still here.

I was able to reproduce the crash in 4.16 and 4.17 as well:

here is test project (test project from Sean Flint)

1) just open the project and fire play

2) take a cup of coffee and wait a couple of minutes :)

Blueprint will cycle showing/hiding sublevel every 2secs until engine will crash with following error:

Assertion failed: WorldSettings [File:D:\Build\++UE4+Release-4.17+Compile\Sync\Engine\Source\Runtime\Engine\Private\Level.cpp] [Line: 435]

in log you will find several warnings like this:

LogNet: Warning: UActorChannel::ProcessBunch: SerializeNewActor failed to find/spawn actor. Actor: WorldSettings /Game/Developers/massi/Collections/UEDPIE_2_SubLevel.SubLevel:PersistentLevel.WorldSettings, Channel: 10 LogNet: Server connection received: ActorChannelFailure

Our project crash any time a level is reloaded with same stack trace....

Is this a bug or I'm doing something wrong? Any suggested workarounds?

Thanks in advance


Product Version: UE 4.17
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asked Aug 24 '17 at 12:54 PM in Bug Reports

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275 4 11 26

avatar image Curs0 Aug 24 '17 at 01:31 PM

it is seems like worldsettings is garbage collected after a minute then assert fails and game crash

EDIT: warning seems to fire if client hides level after it's already been hided server-side

avatar image Curs0 Aug 27 '17 at 08:02 AM

adding a delay before hiding levels server side seems to have solved the problem but it's weird workaround and I'm not able to stream levels independently client side

pls help

avatar image Curs0 Sep 01 '17 at 02:04 PM

any chance to have this answered? thanks in advance

avatar image Rudy Q ♦♦ STAFF Sep 27 '17 at 02:44 PM

Hello Curs0,

After running the project for a couple of hours I did not hit a crash. I have a few questions for you that will help narrow down what issue it is that you are experiencing.

Quick questions:

  1. Can you reproduce this issue in a clean project?

  2. If so, could you provide a detailed list of steps/project so that we can reproduce this issue on our end?

  3. Could you provide screen shots of any settings/blueprints (if provided steps) that may be involved with this issue?

  4. Could you provide your complete callstack including machine ID/ login ID?

  5. Could you try and reproduce this issue in 4.17.2/4./18 preview 1?

avatar image Curs0 Sep 27 '17 at 06:07 PM

Hi Rudy,

happy to hear from you

I can confirm that project crashes even in 4.17.2

It seems I forgot to set 2 players in multiplayer options


1- open given project in editor

2- set number of player = 2

3- press play

4- wait for a couple of minute until editor crash (you will notice mentioned warnings in log immediately)

Submitted crash a couple of minutes ago with machine&login ids



avatar image Curs0 Sep 27 '17 at 06:08 PM

call trace:

Assertion failed: WorldSettings [File:D:\Build\++UE4+Release-4.17+Compile\Sync\Engine\Source\Runtime\Engine\Private\Level.cpp] [Line: 435]

UE4Editor_Core!FDebug::AssertFailed() [d:\build++ue4+release-4.17+compile\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:349] UE4Editor_Engine!ULevel::SortActorList() [d:\build++ue4+release-4.17+compile\sync\engine\source\runtime\engine\private\level.cpp:438] UE4Editor_Engine!UWorld::AddToWorld() [d:\build++ue4+release-4.17+compile\sync\engine\source\runtime\engine\private\world.cpp:2143] UE4Editor_Engine!UWorld::UpdateLevelStreamingInner() [d:\build++ue4+release-4.17+compile\sync\engine\source\runtime\engine\private\world.cpp:2780] UE4Editor_Engine!UWorld::UpdateLevelStreaming() [d:\build++ue4+release-4.17+compile\sync\engine\source\runtime\engine\private\world.cpp:2846] UE4Editor_Engine!UGameViewportClient::Draw() [d:\build++ue4+release-4.17+compile\sync\engine\source\runtime\engine\private\gameviewportclient.cpp:1223] UE4Editor_Engine!FViewport::Draw() [d:\build++ue4+release-4.17+compile\sync\engine\source\runtime\engine\private\unrealclient.cpp:1198] UE4Editor_UnrealEd!UEditorEngine::Tick() [d:\build++ue4+release-4.17+compile\sync\engine\source\editor\unrealed\private\editorengine.cpp:1853] UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [d:\build++ue4+release-4.17+compile\sync\engine\source\editor\unrealed\private\unrealedengine.cpp:402] UE4Editor!FEngineLoop::Tick()

avatar image rz1974 Nov 03 '17 at 05:51 AM


I have same issue here. I play cinematics both client and server independently. When "Level Visibility Track" has visible or hidden key, the warning will appear.

"Warning: UActorChannel::ProcessBunch: SerializeNewActor failed to find/spawn actor. Actor: WorldSettings /Game/Developers/massi/Collections/UEDPIE_2_SubLevel.SubLevel:PersistentLevel.WorldSettings, Channel: 10 LogNet: Server connection received: ActorChannelFailure"

And sometimes it will crash after a while. At the same place Engine\Source\Runtime\Engine\Private\Level.cpp

avatar image masmil1988 Apr 01 '19 at 10:51 AM

Any suggestion on how to solve it in UE versions previous to 4.22?

avatar image Curs0 Apr 01 '19 at 05:14 PM

just avoid to unload a level from server if clients are still using it

avatar image masmil1988 Apr 02 '19 at 09:19 AM

Is there a clean way to wait all clients have executed an event? I wouldn't use delays...

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1 answer: sort voted first

I was able to reproduce this issue on our end. I have written up a report and I have submitted it to the developers for further consideration. I have provided a link to the public tracker. Please feel free to use the link provided for future updates.

Link: https://issues.unrealengine.com/issue/UE-50443

Make it a great day

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answered Sep 27 '17 at 08:14 PM

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Rudy Q ♦♦ STAFF
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