Before I start dismantling things, could someone tell me how the seat bar mechanism is supposed to latch in the up position when the machine is not in use. Mine had been working, but now it won't stay up. I'm wondering if something is worn too far. I see the parts in the parts manual but can't find any mention of it in the service manual, although maybe I'm missing that section. Not sure how that flat triangular piece of metal is supposed to move. Thanks.