If you try and move a vertex of a polygon drawn with the connected lines tool, the behavior is inconsistent. The point will move, but then, for no good reason, the whole object will move. Make a triangle with the snap to grid on and try to move a vertex around. Works fine with snap off, but with snap on, the whole triangle will start jumping around.

(When trying to edit bit paths for pocket cut outs with snap at high resolution (1/16 or 1/32) this bug suddenly moves the whole pocket and you have to use undo to recover the original position of the pocket.)