MS 3 is so buggy it's nearly unusable
I've had to revert to MS 2 because I've found MS 3 to have so many serious, program-crashing bugs as to render it nearly unusable. Also, works created in MS 3 cannot be uploaded to YouTube. I will try the next iteration, but they clearly released 3 without proper testing.
Comments
If you leave without reporting the bugs you found, you're severely reduce the chance of them getting fixed
In reply to If you leave without… by Jojo-Schmitz
Have you take a look to your "repaired" score (with explanations) in this comment? https://musescore.org/en/node/283491#comment-893013
So, this one: 1 Piano Trio.mscz
In your case now, knowing the reason, you can completely prevent this from happening again (while waiting for the fix). And as updates are frequent, it will be ancient history in the near future.