Musescore 3 won't stop crashing with one of my files

As the title says. I can have it open for up to 5 minutes- musescore will crash every time I try to save and also randomly when I try other things. It'll let me add a few notes and then crash when I try and play, for example. I can copy notes from the score into another, but it will crash soon after. Other files are fine.

I have spent the last 4 months working on this and at least 200 hours of my time. It's really quite important to me and I have no idea what I can do. The score is really long (3000 bars ish I think) which is probably causing the issues but at this point I can't copy paste the individual sections into separate scores because it crashes before I make any real progress. I have absolutely no idea what to do.