Your mechanism is two round discs (magnets or magnetic metal) set into the edge of the circular base of the arm wand, (one of which is visible in the photo below), they move as the arm pivots, but are fixed in place.
Item 1 in the photo adjusts a magnetic metal or a magnet that is simply moved closer or further away from those two round items, i.e. whatever you cannot see that moves gets closer or further away increasing or decreasing magnet attraction. As the arm pivots, the 1st magnet moves out of range as the 2nd magnet moves within range.
I would think you could ascertain what moves in or out, and if it is moving properly. You might be able to back it all the way out of it's threaded hole.
Did anything fall out, get it's polarity reversed? The two round elements, could they have been put in 'backwards', i.e. their polarity reversed?
I would ask REED,

