have you done the service bulliten on it yet? They sent me out another main board and i had to return the old one. The put some jumper wires on the board and the resets are gone. Played fine for a year before it started having this problem as well.

You need to find a distributor that will get stern to send out the replacement parts and then you send the old ones back to your distributor and they send them back to stern if i remember correctly. You can try and do it on your calling stern but i had no luck that way.

here it is:

http://www.sternpinball.com/upload/downloads/sb163.pdf