Crashing when saving
I keep trying to save my file but the minute the "save as" window opens it crashes with the message "musescore has stopped responding". When I go back in, my score is there but I have no way of exporting it or saving it. It happens with exporting too. I can't provide the file because of the situation too.
Comments
If the score is there when you start MuseScore again, it clear is already saved, so you could try attaching that. But my guess is, what you are seeing is not your actual copy of the score, but rather the "autosave" copy recovered after the last crash. If you had already saved it recently before the crash, no big deal, just keep using the real copy (by opening it directly). If it had been a long time since the last successful save, the autosave is indeed probably what you want. You can find that and attach it here by checking the info in https://musescore.org/en/node/52116. But I can also guess the issue might be one or corrupt parts within the score, and that delete the parts via File / Pats might allow for a successful save. You can then easily regenerate them, but you'll have lost any custom formatting you did there.
Can you save another (different) file that is open in MusScore?
+1.
Happen to me too while I was exporting XML - crashed out of the blue.
Fortunately, I hit save before it crashed.
In the following try, it's done well.