Adding erroneous accidental marks
1) Select a chord, say a tri-tone.
2) Use arrow key to change pitch of the chord.
3) Notice that MS3 has likely added an accidental mark that does not match the chord. This is insidious and has resulted in a lot of time on my part hunting to find all the instances of this error. It is infuriating to discover these errors well after the fact of their commission. IT doesn't seem to happen all the time, unfortunately.
The workaround is to carefully watch any change of a chord and manually verify and revert notes of the chord into proper tone as frequently required
This has resulted in an embarrassing situation with a pianist who was just paying what was written.
It's seriously irritating to have to put up with this bug. At this point I consider the error to be of type Major because MS3 is generating the incorrect music with a valid input when processing a valid use case.