Keywords: UE4, GC, Crash, UPROPERTY(), AddToRoot

Crash callstack:

Fatal error: [File:D:\Build\++UE4\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\GarbageCollection.cpp] [Line: 623] Invalid object in GC: 0x000001eb2e659900, ReferencingObject: Image /Engine/Transient.GameEngine_0:TDGameInstance_0.CombatMainUIBP_C_0.WidgetTree_0.MiniMapUIBP_1216.WidgetTree_0.Image_0, ReferencingObjectClass: Class /Script/UMG.Image, Property Name: ResourceObject, Offset: 480, TokenIndex: 11

UE4Editor_Core!FDebug::AssertFailed() [d:\build\++ue4\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:425]
UE4Editor_CoreUObject!TFastReferenceCollector<1,FGCReferenceProcessor<1>,FGCCollector<1>,FGCArrayPool,0>::ProcessObjectArray() [d:\build\++ue4\sync\engine\source\runtime\coreuobject\public\uobject\fastreferencecollector.h:697]
UE4Editor_CoreUObject!TFastReferenceCollector<1,FGCReferenceProcessor<1>,FGCCollector<1>,FGCArrayPool,0>::FCollectorTaskQueue::DoTask() [d:\build\++ue4\sync\engine\source\runtime\coreuobject\public\uobject\fastreferencecollector.h:378]
UE4Editor_CoreUObject!TGraphTask<TFastReferenceCollector<1,FGCReferenceProcessor<1>,FGCCollector<1>,FGCArrayPool,0>::FCollectorTaskProcessorTask>::ExecuteTask() [d:\build\++ue4\sync\engine\source\runtime\core\public\async\taskgraphinterfaces.h:829]
UE4Editor_Core!FTaskThreadAnyThread::ProcessTasks() [d:\build\++ue4\sync\engine\source\runtime\core\private\async\taskgraph.cpp:936]
UE4Editor_Core!FTaskThreadAnyThread::ProcessTasksUntilQuit() [d:\build\++ue4\sync\engine\source\runtime\core\private\async\taskgraph.cpp:801]
UE4Editor_Core!FTaskThreadBase::Run() [d:\build\++ue4\sync\engine\source\runtime\core\private\async\taskgraph.cpp:516]
UE4Editor_Core!FRunnableThreadWin::Run() [d:\build\++ue4\sync\engine\source\runtime\core\private\windows\windowsrunnablethread.cpp:76]

Reason:
Some assets object in memory (RAM) not be persisted.

Solution:
Use UPROPERTY() or AddToRoot() to persist assets in memory.

黄沙百战穿金甲，不破楼兰誓不还。——《王昌龄·从军行七首·其四》