The program just abort

Sometimes the program just abort when I try to put in or change things. For example it abort when I try to change from 4/4 measure to 2/4 measure.
It also abort when I try to put in a new measure.

I am using Musescore 3 version.

Is there any known reason for this or any remedy for how to solve the problem?

Ref enclosed file. In part B I want to change measure 26 from 4/4 to 2/4.