I think I might have found a fix for the crash. I don’t really understand it though, but it must be somehow related to my static pointer after all.
The thing is: inside my game instance derived class’ (UStratGI) constructor, I set the static UStratGI-pointer UStratGI::Instance to “this”. I don’t know why I started having crashes now, and not before. However, I added a check to the constructor that makes sure that the instance is not one of those internal default objects, but the “real thing”. Like I said, I don’t really understand how, but the crashes appear to have stopped. For now…