First thing is to check the play, if the arm in front of the dish moves more than 5-7mm either side of centre by pushing it left and right (before theres resistance ) then its time to replace the gearbox. Nothing cheap you can do to repair it unless you own a lathe.
If its within tolerance, its worth trying a couple of tests with a marker (long stick) bolted to the dish, and use the 'centre' command. Mark where the dish stops. Now set a couple of satellite positions in the memory and put these marks on as well See whether the marker always returns to the same positions as well as back to centre. If it does not then the internal sensor is on its way out (Wolsty I believe had a similar problems in March)
Lastly the receiver - I doubt the command structure of the firmware would cause mis pointing, but Im open to a 'first'