I also happen to have a similar issue. Here’s my case: There is an ActorComponent in an Actor blueprint, and this ActorComponent contains an Instanced TMap<FName, UDamageData>. Every time I restart PIE, there’s a high probability that the data inside the TMap fails to be properly serialized. My temporary workaround was to change the creation of the ActorComponent from being created in the blueprint to being created in the C++ constructor, which seems to have resolved the issue. I can’t upload our project’s engineering files, but when I tried to reproduce the problem with a minimal Unreal project, I failed because it’s an intermittent issue.