at the bottom of the filter casing on my 2002 model 107 there are 3 holes, center one large 2" or so, left one is about 1". To the right , looks like a hole but is solid and has a metal shaft in the center that has about an 1" of vertical play. I found a rubber coated nub in the screen at the hot tub bottom that looks like it rusted off from the top of the aforementioned shaft. The motor works fine but sounds laboured. What is the shaft thing? Is this something that controls H2O flow?