The player one 100 point reel switches are likely out of adjustment. Try pulling out the 100 point reel from player 2 100's reel and compare the switch positions to the player 1 100 reel as you cycle through the numbers. There are 3 positions for these switches: Position 1 at "0", position 2 "1-8" and position 3 at "9". Below is a link with some good pictures.

https://homepinballrepair.com/em-score-reels-gottlieb/

The bonus on this game is usually difficult to dial in. I've recommend the following:
1. Clean the rivets on the bonus stepper (under the play field) so that they look clean like the ones on your player unit. Also check the alignment on the stepper.
2. When a drop target drops it hits 2 switches. One is a switch the temporarily closes that triggers the immediate 500 points and a 2nd switch that remains closed and is used in circuit with the bonus stepper to score the end of ball bonus. Make sure the switches that remain closed when the drop target is down are clean.
3. If you are still having an issue you may want to check the travel of the plunger at the bonus unit to ensure you are getting 1 clean step each time it moves.

Also, is normal that the bonus unit steps 15 steps when each ball ends. This is the scan of the 15 pool balls for the bonus. Note the bonus stepper has two speeds...fast for pool balls(targets) not down and slow for targets that require scoring.

You might try cleaning the contacts on the score reel switches. I use a metal Revlon nail file with a rubber handle.

The center switch on the score reel is used in the reset process. Although it appears properly ajusted, you could try pulling the reel out during reset and applying a bit of force on the center switch contacts.. or stick a metal file or a flathead screwdriver between the two switch leafs. Getting that reel to reset might cure the issue with the ball not getting kicked out to the shooter lane.

Not sure if I'm helping or not, but there's been a few topics about the bonus system for this game. I spent quite a bit of time adjusting and cleaning relays and nothing seemed to get mine 100% right until someone suggested adjusting the travel of the metal plunger that gets pulled into the coil on the bonus stepper. The adjustment is make by loosening the fasteners that hold the coil in place. Once loose, the coil can be moved slightly up and down. I had to adjust the coil so that each step advanced the stepper once. This stepper is very fast and sometimes is was skipping a position causing the bonus count to be lower than expected.

You might try advancing the player unit a couple steps manually and trying to restart.

Based on the start up sequence, the start button is triggering the score motor..so you are good through step 3. Is he SB1 relay tripping(on the reset bank)? If not, check switch 2C on the score motor and the switches on on the "S" relay.

If at any time you've loosened the wing nuts on the reset bank and pivoted the bank up o check the witches, make sure reset bank back in its home position and the wing nuts are tight. If the reset bank switches are not straight and tight in its frame, there will be problems.

C=The upper disk level. 2=the switch position as labeled on your score motor(if it hasnt fallen off or isnt covered in grime). Here is a chart that may help:

https://www.google.com/search?q=gottlieb+score+motor&client=ms-android-americamovil-us&prmd=insv&sxsrf=ALeKk02uWJaB-4-S0Lny1SJwaIFzNqkRhg:1622581611878&source=lnms&tbm=isch&sa=X&ved=2ahUKEwj5zuDEq_fwAhVMmeAKHUgXAUkQ_AUoAXoECAIQAQ&biw=360&bih=560#imgrc=KTvnVruaVcohPM

Here is a photo of my Hot Shot(4 player) and the c2 area between my fingers). Check all switches at c2.
20210601_171712 (resized).jpg

Step 7 of the start up sequence indicates the 2nd player relay, (pb) on the reset bank, is triggered when you press the start button a 2nd time through a switch on the score motor at c2. I'd recheck all of the swiches at c2 to make sure the points are clean and making contact. Also check the wires to those switches..

There should be a coil on PB. There should also be a bar that chages the state of the switches on PB. I might be able to help with these missing parts, but i think we will need help understaning how to wire the relay coil.

What is funny, to me, is that I bought a parts reset bank years ago because someone had harvested parts off my Big Shot.

Pm me if you want to proceed with the missing parts..coil and armature/spring. Ill send free..you cover postage.

It should look like the one to its left. You might be able to play a 2 player game by manully changing the position on the two switches at pb.

Hopefully someone with a chart will share so that we might get an idea of why this was hacked. Based on this photo though, I agree the blue wire should go to 2c.

https://imgproxy.pinside.com/RsTgMOLnHQHvwmcfpabQr1kGuQvLnOUDw0YpF02ceCQ/rs:fit:2048:2048/q:70/aHR0cHM6Ly9vLnBpbnNpZGUuY29tL2QvODcvZmUvZDg3ZmVjMTcwNGVlYTIzOTczMDJiZGYxOTllMTc1YzI3YWE2Nzk3MS5qcGc

Does the 3rd switch on 2C score motor look OK? Based on an earlier post, that is the one for the player 2 relay.

There is a make break switch on the first player relay, ZB, that is in circuit to the 2nd player relay. Check all of the make break switches on ZB that are activated after the ZB relay is triggered.

Here is a snip of the schematic (PB is the 2nd player relay)..

2nd player relay pb (resized).JPG

You might also check the start relay "S" at a normally open switch with a maroon white wire.

Last shock I got was by bumping into the flipper button with my body while touching it with my hand. What you did though, is worse because those a full voltage coils..lol

Those end of stroke switches should open 1/8" when the flipper plunger is in the coil. It appears they are adjusted to open too soon..

If you've gaped the end of stroke switch so that it opens as late as possible without resulting in the chatter, the next thing to check is the position of the flipper return spring. The spring should be installed in the position that results in the least upward resistance, but still returns the flipper to its lowest position. You might also try cleaning the end of stroke switches and the flipper switches in the cabinet.

Here is a pic of me manually pushing the flipper plunger into the coil and the resulting gap on the end of stroke switch. The goal is as little gap as possible but not so little that you get the chatter. Id say the gap here is slightly less than 1/8" The coils do not normally ever need to be replaced.

20210606_182032[1] (resized).jpg

Sounds like the player stepper in the head isnt advancing consistantly...might want to check and clean.

You can remove the part with the snowshoes by removing the 3 adjusting screws all of the way.

If the game starts with player one ball one, I'm not sure the issue is the player unit starting starting in the wrong position. Does this always happen in the same pattern, or is this intermittent? If this is intermittent, maybe this is an issue of the stepper occasionally advancing two positions per pulse. Maybe check the travel of the player unit plunger to see if it can be adjusted to ensure one clean step per pulse.

Based on hot shot, you must score a 10 or 100 for the 1st ball relay to trip.

Will the game advance from player 1 ball 1 to player 2 ball 1 if you limit scoring to 10s only?

Id also reccomend checking the player one 1000 point reel switches in all 3 positions.

You might also check the position of the return sping to make sure it is in the position that results in the least upward resistance.

Btw, I like the tip to jumper right to the 25v!

Ill add this era flipper is known to be a bit weak..

I got rid of big shot because i could not get this dialed in. My hot shot works 98% of the time. Ive played others with problems. The change that resulted in the best improvement, for me, was to adjust the length of the plunger travel on the bonus stepper. I feel it's a bad design.

If no points were scored on player ones 1st ball, the game will not advance to player two. Is this what happened?