Are those 4 100,000 pt. relays energized all the time? I don't have a machine here, but I think those relays may be in the head.

If the tilt function is working correctly other than the light, either that switch in series with the light is not closing or making electrical contact, or you have a bad light socket, burned out bulb, or broken wire/connection in that circuit.

Tilt light circuit is pretty simple. I suspect a burn out bulb, or the the tilt relay's switches are not making good contact. Otherwise look for a broken wire, at the bulb, jones plugs, or at the tilt relay.

The 100,00 lights are managed by latch/release relays. These relays have two coil, one to lock and one to release. If they are always on, even at the beginning of a game. check to see if the 100,000 re-latch relay pulls during the reset cycle. (this should turn the light's off) 3rd picture in Red.

Otherwise check if the switches that manage the lights are too close. (1st picture in green)
Or
if the 9th position switch on the score reels are closed at zero instead of open. (2rd picture in Yellow)
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The reset relay is on the Mech. Panel the Latch/reset relay's are in the head.

Because the score reel are resetting correctly (Same switch manage both) I would suspect a broken wire/solder joint.

I would look at the blue-w wire from the reset relay. Check the jones plugs and the latch/reset relay's coils.
I suspect one has become loose.

Also check the black wire. (The other side of the coils).