Steps to Reproduce
  1. Create a WP level (tested with Open World template) to be the server default.
  2. Create another level (doesn't matter if using WP or not) to be the initial starting map for the client.
  3. Go to Play Settings > Advanced Settings...:
    1. Enable "Launch Separate Server"
    2. Play net mode should be "Play Standalone"
    3. Disable "Run Under One Process"
    4. Set "Server Map Name Override" to the level created in Step 1.
  4. Enter PIE. A separate command prompt should be created for the server and the viewport should start in the client map.
  5. In the command line of the editor, connect to the server (by default: "open 127.0.0.1:17777").
  6. Should encounter: "Assertion failed: PIEInstanceID != INDEX_NONE [Link Removed] [Line: 453]"
Callstack
UnrealEditor-Engine.dll!UWorldPartitionLevelStreamingDynamic::FinalizeRuntimeLevel() Line 453	C++
[Inline Frame] UnrealEditor-Engine.dll!UE::Core::Private::Function::TFunctionRefBase<UE::Core::Private::Function::TFunctionStorage<0>,void __cdecl(bool)>::operator()(bool <Params_0>) Line 628	C++
UnrealEditor-Engine.dll!FWorldPartitionLevelHelper::LoadActors::__l23::<lambda_1>::operator()(const FName & LoadedPackageName, UPackage * LoadedPackage, EAsyncLoadingResult::Type Result) Line 526	C++
[Inline Frame] UnrealEditor-Engine.dll!Invoke(FWorldPartitionLevelHelper::LoadActors::__l23::<lambda_1> &) Line 47	C++
[Inline Frame] UnrealEditor-Engine.dll!UE::Core::Private::Tuple::TTupleBase<TIntegerSequence<unsigned int>>::ApplyAfter(FWorldPartitionLevelHelper::LoadActors::__l23::<lambda_1> &) Line 311	C++
UnrealEditor-Engine.dll!TBaseFunctorDelegateInstance<void __cdecl(FName const &,UPackage *,enum EAsyncLoadingResult::Type),FDefaultDelegateUserPolicy,`FWorldPartitionLevelHelper::LoadActors'::`23'::<lambda_1>>::ExecuteIfSafe(const FName & <Params_0>, UPackage * <Params_1>, EAsyncLoadingResult::Type <Params_2>) Line 746	C++
[Inline Frame] UnrealEditor-CoreUObject.dll!TDelegate<void __cdecl(FName const &,UPackage *,enum EAsyncLoadingResult::Type),FDefaultDelegateUserPolicy>::ExecuteIfBound(const FName &) Line 553	C++
UnrealEditor-CoreUObject.dll!FAsyncPackage::CallCompletionCallbacks(bool bInternal, EAsyncLoadingResult::Type LoadingResult) Line 7287	C++
UnrealEditor-CoreUObject.dll!FAsyncLoadingThread::ProcessLoadedPackages(bool bUseTimeLimit, bool bUseFullTimeLimit, double TimeLimit, bool & bDidSomething, const FFlushRequest & FlushRequest) Line 4846	C++
UnrealEditor-CoreUObject.dll!FAsyncLoadingThread::TickAsyncLoading(bool bUseTimeLimit, bool bUseFullTimeLimit, double TimeLimit, FFlushRequest FlushRequest) Line 4996	C++
UnrealEditor-CoreUObject.dll!FAsyncLoadingThread::FlushLoading(int PackageID) Line 7477	C++
UnrealEditor-CoreUObject.dll!FlushAsyncLoading(int RequestId) Line 282	C++
[Inline Frame] UnrealEditor-Engine.dll!UWorld::FlushLevelStreaming::__l2::<lambda_1>::operator()() Line 4419	C++
UnrealEditor-Engine.dll!UWorld::FlushLevelStreaming(EFlushLevelStreamingType FlushType) Line 4426	C++
UnrealEditor-Engine.dll!UWorld::BlockTillLevelStreamingCompleted() Line 4074	C++
[Inline Frame] UnrealEditor-Engine.dll!Invoke(void(UWorldPartition::*)()) Line 66	C++
[Inline Frame] UnrealEditor-Engine.dll!UE::Core::Private::Tuple::TTupleBase<TIntegerSequence<unsigned int>>::ApplyAfter(void(UWorldPartition::*)() &) Line 311	C++
UnrealEditor-Engine.dll!TBaseUObjectMethodDelegateInstance<0,UWorldPartition,void __cdecl(void),FDefaultDelegateUserPolicy>::ExecuteIfSafe() Line 552	C++
[Inline Frame] UnrealEditor-Engine.dll!TMulticastDelegateBase<FDefaultDelegateUserPolicy>::Broadcast() Line 204	C++
UnrealEditor-Engine.dll!TMulticastDelegate<void __cdecl(void),FDefaultDelegateUserPolicy>::Broadcast() Line 881	C++
UnrealEditor-Engine.dll!AWorldSettings::NotifyMatchStarted() Line 315	C++
UnrealEditor-CoreUObject.dll!UFunction::Invoke(UObject * Obj, FFrame & Stack, void * const Z_Param__Result) Line 6429	C++
UnrealEditor-CoreUObject.dll!UObject::ProcessEvent(UFunction * Function, void * Parms) Line 2143	C++
UnrealEditor-Engine.dll!AActor::ProcessEvent(UFunction * Function, void * Parameters) Line 1108	C++
UnrealEditor-Engine.dll!FRepLayout::CallRepNotifies(FReceivingRepState * RepState, UObject * Object) Line 4685	C++
UnrealEditor-Engine.dll!FObjectReplicator::CallRepNotifies(bool bSkipIfChannelHasQueuedBunches) Line 2322	C++
UnrealEditor-Engine.dll!FObjectReplicator::PostReceivedBunch() Line 1515	C++
UnrealEditor-Engine.dll!UActorChannel::ProcessBunch(FInBunch & Bunch) Line 3201	C++
UnrealEditor-Engine.dll!UActorChannel::ReceivedBunch(FInBunch & Bunch) Line 2983	C++
UnrealEditor-Engine.dll!UChannel::ReceivedSequencedBunch(FInBunch & Bunch) Line 564	C++
UnrealEditor-Engine.dll!UChannel::ReceivedNextBunch(FInBunch & Bunch, bool & bOutSkipAck) Line 1026	C++
UnrealEditor-Engine.dll!UChannel::ReceivedRawBunch(FInBunch & Bunch, bool & bOutSkipAck) Line 674	C++
UnrealEditor-Engine.dll!UNetConnection::ReceivedPacket(FBitReader & Reader, bool bIsReinjectedPacket) Line 3539	C++
UnrealEditor-Engine.dll!UNetConnection::ReceivedRawPacket(void * InData, int Count) Line 1895	C++
UnrealEditor-OnlineSubsystemUtils.dll!UIpNetDriver::TickDispatch(float DeltaTime) Line 1301	C++
UnrealEditor-Engine.dll!UNetDriver::InternalTickDispatch(float DeltaSeconds) Line 1613	C++
[Inline Frame] UnrealEditor-Engine.dll!Invoke(void(UNetDriver::*)(float)) Line 66	C++
[Inline Frame] UnrealEditor-Engine.dll!UE::Core::Private::Tuple::TTupleBase<TIntegerSequence<unsigned int>>::ApplyAfter(void(UNetDriver::*)(float) &) Line 311	C++
UnrealEditor-Engine.dll!TBaseUObjectMethodDelegateInstance<0,UNetDriver,void __cdecl(float),FDefaultDelegateUserPolicy>::ExecuteIfSafe(float <Params_0>) Line 552	C++
[Inline Frame] UnrealEditor-Engine.dll!TMulticastDelegateBase<FDefaultDelegateUserPolicy>::Broadcast(float) Line 204	C++
UnrealEditor-Engine.dll!TMulticastDelegate<void __cdecl(float),FDefaultDelegateUserPolicy>::Broadcast(float <Params_0>) Line 881	C++
UnrealEditor-Engine.dll!UWorld::Tick(ELevelTick TickType, float DeltaSeconds) Line 1352	C++
UnrealEditor-UnrealEd.dll!UEditorEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 1923	C++
UnrealEditor-UnrealEd.dll!UUnrealEdEngine::Tick(float DeltaSeconds, bool bIdleMode) Line 531	C++
UnrealEditor.exe!FEngineLoop::Tick() Line 5774	C++
[Inline Frame] UnrealEditor.exe!EngineTick() Line 61	C++
UnrealEditor.exe!GuardedMain(const wchar_t * CmdLine) Line 188	C++
UnrealEditor.exe!LaunchWindowsStartup(HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, char * __formal, int nCmdShow, const wchar_t * CmdLine) Line 231	C++
UnrealEditor.exe!WinMain(HINSTANCE__ * hInInstance, HINSTANCE__ * hPrevInstance, char * pCmdLine, int nCmdShow) Line 282	C++

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Fixed
Fix Commit27876301
Main Commit27876301
CreatedApr 10, 2023
ResolvedSep 14, 2023
UpdatedSep 14, 2023