This is an unfortunate engine bug that’s been around since 4.8ish. Epic is aware of it but is having a hard time solving it. With every engine update, it gets a little better but it’s still not perfect. The only thing I can say about this is that source control/backups help. This is mainly caused by circular dependencies in blueprint (c++ classes seem unaffected). With every update, I’m trying to reduce circular dependencies but in some places atm it’s unavoidable. The only real solution to this is to keep putting pressure on Epic to fix this.