Thank you for the answer.
I think your answer only is about the "save as..." question ?
Because otherwise, it does not seem normal since the new small save is corrupt now.
Thats why my question also was if someone can tell me what Data the game is deleting / not saving.
Also like i said i kept an eye on the file size and this never happened before wirh such a big difference so its weird to me how tjis is normal, when it never happend before after only playing a few minutes and not changing anything in CAS or build mode.