Good evening all. I've been sorting out a somewhat neglected Williams Grand prix, and am having a few challenges figuring out the last few bugs.

Got the spinner and bonus mechanisms all cleaned and polished, and am fairly certain that I have the horseshoes in the correct alignments. None of them are ending up in between traces on the boards etc.

My issue is as follows: When the right side stand up switch closes, the bonus counter steps up as expected, however just after it does so, the right side bonus counter also steps up. Also noted, when the top eject hole right side stand up is lit, and the eject hole switch closes, the right side bonus steps up 2 steps instead of one. (left side does not step up in this situation) Left side stand ups both top and bottom act correctly only affecting the left bonus step up.

Beyond this, the top left rollover switch past the left spinner doesn't appear to have any effect at all, although on several occasions after starting a game, and closing that switch, the game actually tilted. Haven't been able to recreate this after the two or three times it did that.

Lastly the 3/5 ball Jones plug is in the 5 slot, but plugging it in the 3 slot, the game seems to have gone haywire, (however I did have the playfield in the upright position, so the spinner switches were probably closed) I haven't gone further with checking this as I'm trying to sort out the right side bonus first. (I know the 3/5 ball jones plug is also interconnected in the bonus relay circuit so I wanted to mention this just in case)

Change relay is energized as I believe it should be, but it doesn't seem to de energize at all. I thought the top left and right upright switches changed this, and the lights by the eject do flip flop correctly now that I've cleaned and rebuilt the match unit in the back box. SO not sure what operates the change relay.

Could really use some guidance on this one. Then I'll tackle the credit unit not stepping up when this is sorted out.

Thanks guys!