Please protect yourself from corrupted scores
It is saddening to see the reports of users who have lost hours of work through a corrupted score file. Please fellow MuseScorers, invest a little time in a file versioning strategy and your losses will be minimal.
It is not sufficient to simply save a file diligently when it represents many hours of your time. What if your diligently saved file has an unrecoverable issue?
File issues happen. It's a (hopefully rare) fact of life in the world of computing. A file can become corrupt due to hardware or software failings; it can be accidentally, (or malciously), deleted; you can make changes that you wished you hadn't; computers can die unexpectedly, get lost or even stolen.
It is simply not worth risking hours, (days?, months?), of work by commiting any important file to a single version. This applies to any computer file, not just music scores.
Implement file versioning and backups. It doesn't need to cost you any money, just a small amount of your time.
(You could at least use musescore.com uploads as a backup for scores, even ones that are not finished. It is not necessary to make your uploads public and you don't need a pro account.)
Here's a short and clear article on file versioning principles:
https://filestage.io/blog/file-versioning/