I had an issue with this crash, due to some not initialized pointer of an Array to UMaterialInterface* which was also a replicated property.
I’m posting this because the error was really not helpful to understand where it was coming from.
[2020.11.22-16.03.55:477][979]LogWindows: Error: [Callstack] 0x00007ffcaca4b468 UE4Editor-CoreUObject.dll!UObjectBase::IsValidLowLevelFast() [c:\unrealengine\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:284]
[2020.11.22-16.03.55:478][979]LogWindows: Error: [Callstack] 0x00007ffcac92d9f5 UE4Editor-CoreUObject.dll!TFastReferenceCollector<0,FGCReferenceProcessor<0,0>,FGCCollector<0,0>,FGCArrayPool,0,1>::ProcessObjectArray() [c:\unrealengine\engine\source\runtime\coreuobject\public\uobject\fastreferencecollector.h:685]
[2020.11.22-16.03.55:479][979]LogWindows: Error: [Callstack] 0x00007ffcac8ce80a UE4Editor-CoreUObject.dll!FRealtimeGC::PerformReachabilityAnalysisOnObjectsInternal<0,0>() [c:\unrealengine\engine\source\runtime\coreuobject\private\uobject\garbagecollection.cpp:1045]
[2020.11.22-16.03.55:480][979]LogWindows: Error: [Callstack] 0x00007ffcac91228e UE4Editor-CoreUObject.dll!FRealtimeGC::PerformReachabilityAnalysis()