Multiple users have reported the game corrupting and losing save data, which is a particular blow if progress is being made in the My Career mode - some of those encountering the problem have taken to Reddit. We also know this can happen from experience; our reviewer has encountered the issue and was less than impressed. Part of the problem is that the error automatically overwrites the corrupted file, so data not residing on online servers is lost.
It should be noted that this doesn't seem to be a Switch-only issue; the main Reddit page for the game has multiple threads related to the problem on other hardware. 2K is reportedly aware of the cause and is working on a patch, though we've reached out to the studio for comment regarding the position with Switch.
Hopefully it'll be resolved soon; have you encountered the problem?