haven't mentioned the age of the deck, so assuming it is in use for some time. it has to do with the bearing well, assuming that the ball is in place, the bush may have sunk slightly over time (ball wear is rare but could also be a factor). Common fixes for this issue are (1) use a washer of suitable thickness over the existing bush or (2) change the ball to a marginally bigger one. For both (1) and (2). These balls can be easily bought at any 2 wheeler spare-parts shop. One word of caution, when implementing this fix, keep an eye on the resulting rise of the sub-platter over the plinth surface. If the height increase is evident over the default height setting, then the tonearm height will also need to be calibrated accordingly. Hope this helps.