Sound is muted continuously

Hi all,
I'm modifying one of my first compositions - a solo piano - which was pretty simple and wherever I change some notes to add triplets or more notes to the mesure, it stops reproducing my score the measure after the modifications. In the last 5 minutes I had to close and reopen the software 3 times, and it's really annoying.
I'm using the last version of Musescore with new Muse Sounds on a Macbook Pro. What's wrong here? Can I do anything?
I also work with Logic on 30 tracks projects and never had the problem, so it's not my Mac.
Thanks!