musescore tremblement acting up

Hi all,
I downloaded this score from musescore. Starting on measure 14 there is a tremblement. I separated the (Accordion 2); when when it plays back, the notes sustain across the whole measure and some times it sustains across till the end. Is this behaving as designed or I missing something here. Please see the attached musescore file.

There are other issues with this downloaded score, such as it shows accordion but plays viola but I can feel my way to fixing it but my issue is the tremlement.

Thank you,
Robert