Notes get stuck on playback

Sometimes when I stop playback notes get stuck, ie. don't stop playing (I'm using internal synth). To me, it seems that this happens completely randomly. It happens in all my sessions, so I really can't give steps to reproduce this bug.

It would be very helpful (apart from the bug being fixed) that there was also kind of panic switch, which sends all notes off command.

I'm using mscore version 1.0