The only mechanical issue could be if a part is missing or stuck, take a look at the top thread on driver alarms and pump cleaning. Often I see the upper bearing 3000.610 or the oring 3000.612 are missing (lost at some point in cleaning) or the parts inverted, red oring is on top of the bearing, it should be below the bearing. It is also possible to have the bearing stuck to the drive unit with calcium deposits.