Unreal Engine Issues and Bug Tracker (UE-58016)

Description

A crash occurs when switching back and forth between levels when using seamless travel. This happens if a multicast was called and if it contains a member variable.

Steps to Reproduce

Download the attached project
Open the project
Open the advanced play settings
Set the number of players to 2
Uncheck "Use Single Process"
Set "Editor Multiplayer Mode" to "Play As Listen Server"
Play in Stand alone
Click one of the windows to insure that they are focused
Press the 'j' key to call the multicast custom event
Press the '2' key to change maps (to level 2)
Press the '1' key to change maps (to level 1)

Result: The Standalone windows will crash when navigating back to the first map
Expected: The levels would change back and forth with no issues

Callstack

Fatal error: [File:D:\Build\++UE4+Release-4.19+Compile\Sync\Engine\Source\Runtime\Engine\Private\BlueprintGeneratedClass.cpp] [Line: 196] UBlueprintGeneratedClass::GetAuthoritativeClass: ClassGeneratedBy is null. class '/Game/Map1.Map1_C'

UE4Editor_Core!FDebug::AssertFailed() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:419]
UE4Editor_Engine!UBlueprintGeneratedClass::GetAuthoritativeClass() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\engine\private\blueprintgeneratedclass.cpp:196]
UE4Editor_UnrealEd!FMemberReference::ResolveMember<UFunction>() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\engine\classes\engine\memberreference.h:319]
UE4Editor_UnrealEd!`anonymous namespace'::FixOverriddenEventSignature() [d:\build\++ue4+release-4.19+compile\sync\engine\source\editor\unrealed\private\kismet2\blueprinteditorutils.cpp:6167]
UE4Editor_UnrealEd!FBlueprintEditorUtils::ConformImplementedEvents() [d:\build\++ue4+release-4.19+compile\sync\engine\source\editor\unrealed\private\kismet2\blueprinteditorutils.cpp:6238]
UE4Editor_Engine!UBlueprint::PostLoad() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\engine\private\blueprint.cpp:775]
UE4Editor_CoreUObject!UObject::ConditionalPostLoad() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\uobject\obj.cpp:994]
UE4Editor_CoreUObject!FAsyncPackage::PostLoadObjects() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\serialization\asyncloading.cpp:6281]
UE4Editor_CoreUObject!FAsyncPackage::TickAsyncPackage() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\serialization\asyncloading.cpp:5545]
UE4Editor_CoreUObject!FAsyncLoadingThread::ProcessAsyncLoading() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\serialization\asyncloading.cpp:4468]
UE4Editor_CoreUObject!FAsyncLoadingThread::TickAsyncThread() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\serialization\asyncloading.cpp:4979]
UE4Editor_CoreUObject!FAsyncLoadingThread::TickAsyncLoading() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\serialization\asyncloading.cpp:4714]
UE4Editor_CoreUObject!ProcessAsyncLoading() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\serialization\asyncloading.cpp:6873]
UE4Editor_CoreUObject!StaticTick() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:489]
UE4Editor_Engine!UGameEngine::Tick() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\engine\private\gameengine.cpp:1220]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:3339]
UE4Editor!GuardedMain() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\launch\private\launch.cpp:166]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
UE4Editor!WinMain() [d:\build\++ue4+release-4.19+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253]
kernel32
ntdll

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Won't Fix

Component	UE - Gameplay - Blueprint
Affects Versions	4.19.1

Created	Apr 20, 2018
Resolved	Aug 18, 2021
Updated	Aug 18, 2021

View Jira Issue

UE-58016

Crash When server traveling from one level and then back again after calling a multiclass event (using Play as Listen Server)

Crash When server traveling from one level and then back again after calling a multiclass event (using Play as Listen Server)

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