UE-51948 crash Assertion failed: NewWorld LoadMap()

Dear Epic Staff and Community,

I have important research to contribute to a crash that occurs when a client tries to leave a networked match and tries to load a map:

It was happening to me after upgrading from 4.11 to 4.18, it has been reported since 4.15

I finally narrowed it down to a simple repro case

Simple Repro Case

  • make a new level

  • Add a boolean variable in the Level Blueprint, make it repnotify

  • Now start a multiplayer game (I use commandline, not PIE)

  • Have the client leave the match (or dc them from the server, or have server quit, etc)

When client leaves the match (or is disconnected for some reason) and tries to load the same level that the server was hosting (or any level it seems)

I get this crash

Assertion failed: NewWorld [File:D:\Build\++UE4+Release-4.18+Compile\Sync\Engine\Source\Runtime\Engine\Private\UnrealEngine.cpp] [Line: 10494]

UE4Editor_Engine!UEngine::LoadMap() unrealengine.cpp:10496 
UE4Editor_Engine!UEngine::Browse() unrealengine.cpp:9948 
UE4Editor_Engine!UEngine::TickWorldTravel() unrealengine.cpp:10137 
UE4Editor_UnrealEd!UEditorEngine::Tick() editorengine.cpp:1605 
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() unrealedengine.cpp:396 
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:3296 
UE4Editor!GuardedMain() launch.cpp:166 
UE4Editor!GuardedMainWrapper() launchwindows.cpp:134 
UE4Editor!WinMain() launchwindows.cpp:210 
UE4Editor!__scrt_common_main_seh() exe_common.inl:253 
kernel32!BaseThreadInitThunk() 
ntdll!RtlUserThreadStart()

If I remove the repnotify var (which I wasn’t actually setting or changing, it was just in the var list), the client crash goes away

#:heart:

Rama

Hello,

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Thanks