Opened door after wash and found upper sprayer arm lying loose and can't figure out how to reinstall it. It's the whole unit, not just the part that spins but the "spinner" and the arm to which it is attached. There are 2 holes in the back of the sprayer arm that seem to align a water inlet and "male" guide "button" on the back interior surface of the machine but I don't see how the sprayer arm snaps to anything to stay in place. Is the arm to remain attached to the back wall when the top rack is rolled in and out, or is the arm attached to the rack and moves back and forth with the rack? If it's to remain attached to the back wall, what's the trick for re-attaching it? Thanks.