It always was. ;) Some people had issues the way it was before, then people had massive issues with the prior patch, and now it seems other people have issues (again) with the latest patch.

Valheim dumps the entire world file instead of using a database like Conan: Exiles where only minimal changes need to be saved.

That's most likely what causes Steam Cloud to choke and throw up, taking everything else with it.

Turn it off, and your life will be much easier. Not only in Valheim.