Welcome to EM
Good morning jgeiger -
Nice vid collection. For the most part I was part of that generation and at the tale end of EM. However EM is my passion. Bowlers are the jewel of most EM collectors and their collections. I didn't sleep at night until I owned one. It's kind of like a Star Wars Cockpit HUO would be to your vid collection.
Nevertheless I wish I could tell you to go to this specific segment of the game for the fix but it's a bit more complicated than that. So I'll give you some starting points. The video below is courtesy of the pinrepair website. I'd suggest that you'd watch this you tube video as your stepper units have everything to do with game play. Furthermore spend some time from start to finish reading/learning about EM.
The buzzing could be the fingers on the step unit in between two rivets. It also could be a bad coil. I want you to start at the stepper units.
The overall condition of your game is relevant to how it will run. The key culprit is years of solidified oil that is now glue. This causes these stepper units to seize up and they MUST move freely.
I'll caution you when you tackle these units take pics if you have a smart phone or camera so you know how they look before during your disassembly. Especially when your first learning. A magnetic tray, 90 plus percent alcohol, 400 to 600 grit sand paper, a small scrub brush, and time. My grandfather said only one way to learn and that's to do.
Could this also be a dirty contact or coil. Yes but irregardless if your step units, and I know you have many in a bowler, are not moving freely your game will never work right. That means zero resistance like in the attached video.
EM machines are like wind up watches once you bowl and progress through your game all the parts move from the time the game begins until the game is over.
I wish you luck and remember bowlers are the most collectable out of any EM. Who didn't dream of having an alley in their basement when they were kids.
OHEMIO