Good advice here. Both of these are the first place I'd check. Especially those score reels. I know you said you checked 'em but I've had to go over mine 3 or 4 times sometimes to get them working correct. They looked good but a 3rd cleaning of the 0 position got them going again. Stepper motor contacts are notorious as well.

Edit: I don't know how yours is set up but could that 100 relay be firing because it is trying to resest the 100 wheel on one of the scores?

Wow the player stepper really looks like it could be your problem. If it isn't then it is it's own problem since you are having to push the disk manually to reset it. It should spin freely back to home not sit there till you put pressure on it like I saw on the end of the video. Unless that one is a single step back and somehow you put enough pressure to make it spin. I'm not the expert DirtFlipper or some of the other guys are as they are the ones that help me. Seeing the video tells me I would start with that stepper unit though.

I pictured this as unplayable and up on a rotating display like a prototype car at a car show. Doesn't need a 1000 fingerprints all over it.