Assertion failed: IsNetMode(NM_ListenServer) || IsNetMode(NM_DedicatedServer) [File:\Engine\Source\Runtime\Engine\Private\World.cpp] [Line: 3550] > UnrealEditor-Engine.dll!??R<lambda_1>@?1??RemoveFromWorld@UWorld@@QEAAXPEAVULevel@@_NUFNetLevelVisibilityTransactionId@@PEAVULevelStreaming@@@Z@QEBA@XZ() Line 3550 C++ UnrealEditor-Engine.dll!UWorld::RemoveFromWorld(ULevel * Level, bool bAllowIncrementalRemoval, FNetLevelVisibilityTransactionId TransactionId, ULevelStreaming * InOwningLevelStreaming) Line 3624 C++ UnrealEditor-Engine.dll!ULevelStreaming::UpdateStreamingState(bool & bOutUpdateAgain, bool & bOutRedetermineTarget) Line 1042 C++ [Inline Frame] UnrealEditor-Engine.dll!FStreamingLevelPrivateAccessor::UpdateStreamingState(ULevelStreaming *) Line 776 C++ UnrealEditor-Engine.dll!UWorld::UpdateLevelStreaming() Line 4327 C++ [Inline Frame] UnrealEditor-Engine.dll!UWorld::FlushLevelStreaming::__l2::<lambda_1>::operator()() Line 4592 C++ UnrealEditor-Engine.dll!UWorld::FlushLevelStreaming(EFlushLevelStreamingType FlushType) Line 4598 C++ UnrealEditor-Engine.dll!UEngine::LoadMap(FWorldContext & WorldContext, FURL URL, UPendingNetGame * Pending, FString & Error) Line 15112 C++ UnrealEditor-Engine.dll!UEngine::Browse(FWorldContext & WorldContext, FURL URL, FString & Error) Line 14670 C++ UnrealEditor-Engine.dll!UEngine::TickWorldTravel(FWorldContext & Context, float DeltaSeconds) Line 14868 C++ UnrealEditor-UnrealEd.dll!UEditorEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 1989 C++ UnrealEditor-UnrealEd.dll!UUnrealEdEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 550 C++ UnrealEditor.exe!FEngineLoop::Tick() Line 5921 C++ [Inline Frame] UnrealEditor.exe!EngineTick() Line 61 C++ UnrealEditor.exe!GuardedMain(const wchar_t * CmdLine) Line 180 C++ UnrealEditor.exe!LaunchWindowsStartup(HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, char * __formal, int nCmdShow, const wchar_t * CmdLine) Line 247 C++ UnrealEditor.exe!WinMain(HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, char * pCmdLine, int nCmdShow) Line 298 C++ [Inline Frame] UnrealEditor.exe!invoke_main() Line 102 C++ UnrealEditor.exe!__scrt_common_main_seh() Line 288 C++
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-226526 in the post.