Note entry | MuseScore

Musescore 3.6.2, Win 10. When entering notes using mouse (select note location in score and note duration from Note Input Bar, press “N” key to place note). Before I enter the note, a note of the selected duration 18 ledger lines below the staff is entered. in approximately five seconds an additional note 18 ledger lines below the staff is entered. This continues until I either hit “Esc” or “cntrl z”. I an able to move the errant note up to the staff using the arrow keys and I am able to enter additional notes at the same location for chords, but I cannot cause the errant note entry to cease. Mouse performs correctly in all other apps and I have checked the mouse driver. Have reinstalled Musescore 3.6.2 but issue persists. Occurs in attached score (End ReDo). In other scores, notes are added at the approx 5 second interval but not 18 leger lines below staff (drums slowed}.