My parents run an Inglis 1A42000 (I honestly cannot find a better model number) Heady Duty washer and it loves to lose the top half of the agitator if you even THINK of overloading it. It's half in by eight plastic tabs in four guides in the lower half of the agitator and friction. If they ever let go (which happens usually when you overload the machine) and it slips up more than three inches the top half separates from the spinning agitator and the agitator loses the corkscrew motion and snaps off the plastic tabs.
This is followed by the spin cycle where if the agitator has not had a chance to settle back down into the guides it will start bouncing around inside during the spin cycle making a HORRIBLE racket, wrecking the lint screen and if you are not careful when you race downstairs and fling open the top to stop it, one out of three times it will catch on something and launch the agitator across the room.
This is the third one we are on right now. They are $85 each and they have ALL done it. I want to better secure it in place but I still need to remove it to clean the lint screens.
Ah yes! I have encountered this before on friends' machines... The only person I know of who 'solved' the problem (after her second agitator top!) was to mix large and small items in wash loads. It was a pain in the neck not being able to wash a set of sheets in one load, but it worked for her.