It's my ProS back. I've pushed the tab on the back in by hand and ran some paper through and the counter still doesn't wind over to 1, stays on S.. was playing up before doing this sometimes and sometimes not, now all the time, is it a simple fix of reattaching something inside the back? I'd need to get a new screwdriver to open it. My Pro back kicks over to 1 holding in the tab, and just running 120 paper through it fine. So I know it's not the casing not holding it in properly.