Shouldn't be any real problems there. I've used a gorgar sys 6 mpu in a hot tip (first sys 3) for years without issue.

Do you have any other driver/mpu you could swap to see if it's a board issue? Are any of the three PIAs (the biggest chips on the driver) socketed?

Is it a certain switch that reliably causes this?

Start by going into Switch Test.

Take the ball out.

Now, test each switch and make sure the # displayed, matches the # that is supposed to be that switch.

For instance, if you press a target switch, and it displays the number of the Slam Tilt switch, the game will reset....

If switch test doesn't point you at the source of the problem a good next step is to isolate if the issue is play field related or board related.

To do this disconnect the switch row and column connectors at the driver board and run the switch test just using a jumper wire. Use the switch matrix documentation and step thru by starting with connecting your jumper to col 1, then test each row. Move to next col and step across the row and so on. If everything works as expect here you problem is on the play field.