I guess this may be a problem caused by the code related to UE loading packages. This is related to the deserialization of disk files to object memory.
This may also require debugging with tools such as RenderDoc to see whether the ImageDescriptor referenced by those objects that randomly turn black at runtime has uploaded textures to the GPU.
In other words, one check direction is from disk to CPU, and the other check direction is from CPU to GPU.
I know the function about loading packages:
UPackage* LoadPackage(UPackage* InOuter, const TCHAR* InLongPackageName, uint32 LoadFlags, FArchive* InReaderOverride, const FLinkerInstancingContext* InstancingContext)
But I don’t know rendering pipeline in UE.