Why UE 5.5 actor serialization become so slow?

[JaroMast]

In 5.5, the serialization of an actor is hundreds of times slower compared to 5.3. I have a scene with 100 actors with kinda limited saved data (200 bytes each). In 5.3 applying serialization for those actors took few miliseconds. Now the same operation takes 2 minutes!

Code for serialization:

void UMainFunctionLibrary::ApplySerialization(AActor* Actor, const TArray<uint8>& Data)
{
	if (Data.Num() <= 0 || !IsValid(Actor))
		return;

	FMemoryReader ActorReader(Data, true);
	FObjectAndNameAsStringProxyArchive Archive(ActorReader, true);
	
	ActorReader.SetIsLoading(true);

	Actor->Serialize(Archive);
}

TArray<uint8> UMainFunctionLibrary::SerializeActor(AActor* Actor)
{
	TArray<uint8> OutSerializedData;
	if (Actor == nullptr)
		return OutSerializedData;
	FMemoryWriter Writer(OutSerializedData, true);
	FObjectAndNameAsStringProxyArchive Archive(Writer, true);
	Writer.SetIsSaving(true);
	Archive.ArIsSaveGame = true;
	Actor->Serialize(Archive);

	return OutSerializedData;
}

Did UE 5.5 change how it saves data, or what? Loading games from a save file can’t take several minutes, so this is a game-breaking issue.

[JaroMast]

The problem was that actors got filled with a data from previous engine version. For some reasons this generates some additional overload and completely kills the performance.

[KillerJim_UK]

Thanks for the information, trying to load save games and saw performance tank (was old data!)