Have a Chicago Coin Cadillac spare lite ball bowler that has been working fine for years and lately is giving an extra frame at end of game before 'game over'. Frames increment correctly including 10th frame. At end of 10th frame or extra fame if strike or spare in the 10th the game does not go to game over. So rather than going to game over I get one extra frame and then game over. Have not found anything obvious and trying to tack it down with schematic but no luck yet.
Any suggestions would be great.

Thanks John

Well do thanks. Not sure which unit that is as some labels are missing. Went thru all steppers when I got this game which was in storage a long time.

Yes and after that extra shot it goes to game over

Looked over the 10th frame unit and seems to step up ok and resets ok. Not sure on the wiper blade positions they have not been touched in years and game was working without issue. All the fingers appear to have good tension as well. It was not happening all the time so I did a bit more checking today going thru all the 10th frame combinations and listed them below in hope this may shed some light on issue.
10th FRAME
Open results in G.O. correctly
Spare and count results in G.O. correctly
Spare and Strike gives me 2 more balls and then G.O. wrong
Strike and open results in G.O. correctly
Strike and Spare gives me 2 more balls then G.O. wrong
2 Strikes and open results in 2 more ball then G.O. wrong
3 Strikes results in G.O. correctly

Attached a couple pics of the 10 frame unit. One in the home or start position and 2nd in max position.

home (resized).jpg

max steps (resized).jpg

Thanks will look into it tomorrow afternoon

Well 1st and 2nd shot relays and contacts look ok. Tried to clean them a bit but tough to get at them. Noticed I never see 11th frame relay pull in and when 10th is over frame unit may not step up and that's when I get 2 more tries
The seq above for 10th on May not be same every time. I will have to try couple more times

Mopar

Thanks for your help on this one. Did not give up and went back to your original suggestion but this time took a closer look at 10th frame unit and frame unit. Think I found issue with frame unit as rivet is missing/broke off. See attached pic.
Not sure how to fix/replace rivet so open to suggestions

Thanks again

20210726_170728 (resized).jpg