Musescore 3 becaming slower faster than Musescore 2

Is anybody else experiencing this problem? I have a 11 minute long String Quartet file that I started on Musescore 2, and it is completely useless on Musescore 3 due to the massive sluggishness. Also, other works for orchestra became very slow faster than the former version.

Also, not sure if relatable, but the playback is also bugging. It sometimes freezes on one note or start playing on a different measure than the one that I selected, and sometimes even skip measures.

My computer is completelly capable of executing Musescore 3, so I don't believe that is the problem.

Thanks for your attention,