My Hi-Low Ace machine was working perfectly this past October. I covered it up and when I recently fired it up discovered that special feature sticks on when obtained. Sometimes stays locked on till the counter maxes out, sometimes just a few extra games. When the special feature sticks on, the score motor continue to rotate and the alternator relay keeps actuating/ switching the special lights back and forth. The special relay is free and moving easily. I checked the 4 switches that score on a special and they seem in proper position and working order. The game plays perfectly other than the sticking special scores.
The machine is in my shop which is heated with wood. I thought that perhaps some drying occurred and switches were in need of adjustment. To that end I tightened all the screw on the main score motored. I also check that all the Jonas plugs were in tight. No joy. Problem persists.
This machine was DOA when I got it a little over a year ago. With past help from this forum I was able get her back in shape and played hundreds of times.
I would be very grateful for any thoughts on where to looks to fix the current problem. Thanks in advance. Bill

Thanks for responses!
The reset motor is working. If tripped, the relay spins the score motor reliably.
The special relay is staying locked on. Excuse my ignorance, but when you say" score motor 8A switch open", are you referring to the main score motor which has the cams numbered 1-12? If yes, I examined /messed with the stack numbered "8" with possibly some results. Hard to tell. I had a run of tripping a lit special switch of 9 times with things working perfectly. Then on the 10 sequence it ran credits continually till it maxed out at 23. I want to make certain that is the area I should be adjusting. If that is not the area of interest, can you focus me closer. There is another score motor that runs the cards and specials; high /low. Don't wish to make matters worse by fumbling with the wrong switches.
Thanks,
Bill

Bingo!! It was the switch with the orange & red and yellow wire. It is on the 6th score motor cam from the left and marked # 6 on the paper stabled in at the factory.
For my own edification, I would still like to better understand the nomenclature; "score motor 8A switch ".
Thanks to everyone who helped run my problem down.
Best Regards,
Bill/Jawsplow