I have had it happen to me too. I’m on engine source build 4.25.1
I’ve made a custom game instance but also added steam multiplayer into the mix.
Though, this has also happened to me on a seperate project, which was made through launcher 4.25.3. It also had steam multiplayer (although most of it was rewritten) and custom GI.
Mostly crash when pressing PIE or exiting PIE, or even random clicking on stuff after being in editor for a while. Happens only sometimes and have not figured out a way to reproduce this consistently. I’ve also never been able to crash during debug editor mode. Which makes it extra hard to figure out what is happening. I have neither been able to crash in game through launch. Which makes me think this mostly has to do with PIE or development editor mode.
Fatal error: [File:C:/IsakStream/Engine/Source/Runtime/Core/Private/Windows/WindowsPlatformMisc.cpp] [Line: 475] Pure virtual function being called
UE4Editor_Core!PureCallHandler() [C:\IsakStream\Engine\Source\Runtime\Core\Private\Windows\WindowsPlatformMisc.cpp:477]
VCRUNTIME140
UE4Editor_CoreUObject!UGCObjectReferencer::AddReferencedObjects() [C:\IsakStream\Engine\Source\Runtime\CoreUObject\Private\Misc\GCObjectReferencer.cpp:27]
UE4Editor_CoreUObject!TFastReferenceCollector<1,FGCReferenceProcessor<1,0>,FGCCollector<1,0>,FGCArrayPool,0,1>::ProcessObjectArray() [C:\IsakStream\Engine\Source\Runtime\CoreUObject\Public\UObject\FastReferenceCollector.h:635]
UE4Editor_CoreUObject!TFastReferenceCollector<1,FGCReferenceProcessor<1,0>,FGCCollector<1,0>,FGCArrayPool,0,1>::FCollectorTaskQueue::D
https:\/\/forums.unrealengine.com\/core\/image\/gif;base64
oTask() [C:\IsakStream\Engine\Source\Runtime\CoreUObject\Public\UObject\FastReferenceCollector.h:383]
UE4Editor_CoreUObject!TGraphTask<TFastReferenceCollector<1,FGCReferenceProcessor<1,0>,FGCCollector<1,0>,FGCArrayPool,0,1>::FCollectorTaskProcessorTask>::ExecuteTask() [C:\IsakStream\Engine\Source\Runtime\Core\Public\Async\TaskGraphInterfaces.h:849]
UE4Editor_Core!FTaskThreadAnyThread::ProcessTasks() [C:\IsakStream\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:1039]
UE4Editor_Core!FTaskThreadAnyThread::ProcessTasksUntilQuit() [C:\IsakStream\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:863]
UE4Editor_Core!FTaskThreadAnyThread::Run() [C:\IsakStream\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:940]
UE4Editor_Core!FRunnableThreadWin::Run() [C:\IsakStream\Engine\Source\Runtime\Core\Private\Windows\WindowsRunnableThread.cpp:86]