is the tilt trip relay tripping or is the anti-cheat relay not powering/staying powered?

you should be able to turn on the game and manually push down the anti-cheat relay armature/plate and it stays down.

if the anti-cheat relay is powering when the game is first turned on, I assume switch C on it is misadjusted permanently closed? That's one way to prevent credits from resetting at power-on.

if you can manually reset the tilt trip relay by lifting up the armature and it stays in the untripped position, all the slam switches and pendulum bob are ok and the problem is likely the CU 4D switch. It's acting like it's MBB (make-before-break) ... in other words, during it's operation by the cam all three blades are touching each other at the same time. You need to adjust that switch so the center/moving blade disconnects from a surrounding blade before it touches the other surrounding blade. If the moving blade connects wire 13-9 to 14-5, you'll trip the tilt trip relay.

if you want, you could just bend up the top blade on CU 4D so the center blade never touches it. That would disable the "tilt when the coin switch closed too long" circuit and also fix the MBB issue.

has the game always done this, or did it just start?

the anti-cheat relay isn't particularly important...maybe. The only other ways the anti-cheat could power is:
- CU 5C is closed and the EB trip relays aren't tripped. You could manually trip the EB trip relays then turn on the game and see what happens.
- someone changed the circuit or you have a short

if CU 5D is closed and the switch stack is sitting up on a cam lobe, the maybe part kicks in. Why is the stack being lifted?

to narrow things down, if you manually reset the tilt trip relay then turn on the game, what happens? If it trips, it may be worth stuffing some paper under the anti-cheat armature so it can't close and try again. if it still trips, you've got a stuck slam switch, pendulum bob, short or plug installed incorrectly in a socket as mentioned above.

the mixer #2 relay buzzing is common. As soon as you untrip the tilt trip relay, wire 30 is connected to wire 21-3 and much of the 50V circuit can be active. You can try removing the relay armature and whacking it with a hammer on an anvil to flatten it/remove dimples, swap the armature with another relay, swap the coil with one that's not powered as long/often, fiddle with the coil top if it's worn, or replace the coil.

1] the switches behind the buttons

there's multiple switches on the stacks behind each button. One of the switches on each stack - usually the middle one - causes the start relay to power. That switch needs to close as late as possible in the button travel.

You should be able to push in the colored buttons partway and have the lit panel change to that color, then let go and change to a different color without the game cycling....at least for red, green, blue and white. if you are doing it later with yellow, you can probably only flip between yellow and red.

Adjust the button switches to make that happen and see if the blue and green work right. The goal is to have the play scores (blue), play features (green), or play superscores (white) relays power before the start relay does. For the red button, none of the those relays should be powered.

2] on can-can, the red letter feature unit in combo with the other score and feature units causes the stop relays to power at the right time. Take a look at the upper right corner of the schem.

If the selection feature unit is stopping at the right place sometimes but not others, a wiper/rivet connection on the red letter unit is likely bad.

the OK sequencing happens around A-G33 on the schem.....red, yellow, magic screen, selection and finally score booster. If one of the stop relays in that sequence doesn't power, the rest of the OK setup never happens.

in your case, if the selection stop relay doesn't power, the selection feature unit will step forever. The yellow score booster trip relay won't trip either.

cycling the game causes the pos 29 relay to open...that does abort the OK game setup sequence.

3] as bpc said, the wipers need to be centered (more or less) on the rivets at each step. If you bridge to an adjacent rivet, you're sol. If, however, you are also getting other lights stuck on (like feature lights), usual cause of that is a spotting index switch stuck closed.

generally you can't bend the wipers on a stepper unit to align them onto a rivet. The way the wipers mount on the center hub guarantees correct alignment unless someone mangled the wipers.

if all the wipers are off the rivet centers the same way, you need to loosen the screws fastening the contact plate to the unit frame and rotate the contact plate (do this with the wipers on step 1+...the reset position has more slop in where the wipers are). It's okay if the contact plate is cocked wrt to the unit frame, just make sure the wiper contacts are as centered on all rivets as possible.