I have the Rigid 4512 10" table saw and it has been working great until recently. The pulley on the motor shaft is moving to the end of the shaft. I thought at first the set screw was just loose so I checked it. It did not appear to be loose, but I had to loosen it anyway to slide the pulley back into place. I re-tightened the set screw and it was fine for another 30 minutes of use and it happened again. At the moment it seems that there is something else wrong because the set screw is not loose...The key is slipping. I'm not sure what else to try at this point. Any suggestions?