Greetings!
Here is a little bug in the pattern matrix: try to move a track into a different position (no matter which direction), and then without actually moving the mouse pointer, re-click it with LMB; try to move it further: you won’t be able to move the track to the very edge of the matrix in the direction OPPOSITE to your first move. (If you moved the track down, you won’t be able to move it the the topmost row of the matrix; if you moved it left, you won’t be able to move it to the rightmost row of the matrix. And so on.)
Sincerely,
Artur