I was following the regulator checklist, and kindof got stuck at step 11. The cover (and a thin metal washer between the cover and diaphram come of easy enough, but the diaphram doesn't come out easily. It feels like there is a little rubber ring around the edge of the diaphram, I believe it is attached. Am I supposed to disassemble more, or pull harder? Or is every reg different? This is a lesser-known brand sold by Divemar in Canada.