I need to dismantle a Reba Ware dual flush to get to a leaking O ring/flapper. It is part of a Fowlerware system circa 1985. I understand that after dismantling arms to dual flush etc that the unit should respond to downward pressure and turning the unit anticlockwise, like a bayonet fit after which the entire internal mechanism comes away. This model has guides where it locks but NO bayonet locking mechanism. How else could it be locked? Got me beat. There has to be a simple answer but can’t find any more info on the internet tks