Sorry but that was a mistake. This forum is full of posts from people who tried shotgun cleaning & adjustments, and caused more problems than they were originally trying to solve.
What to do instead: Slowly and carefully diagnose one problem at a time and then fix only that.
http://www.pinrepair.com/em/index2.htm#clean

Inspect and diagnose this circuit with Alligator clip jumper wires
http://www.planetimming.com/Pinball/troubleshooting/EM%20Troubleshooting.pdf
http://www.pinrepair.com/em/index3.htm#features
Example of a pinsider actually doing this https://pinside.com/pinball/forum/topic/red-baron-tech-question#post-5858156
Be careful because this circuit runs on 120 volts

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don't worry about it. If ya make things worse, it's just another opportunity to fix something. If you try and make sense of the problem and solution on the schematic, the schem will make more sense over time.

howardR highlighted one circuit path on the schem, but not the ones thru the U relay or E relay switches. See if you can figure out why by looking at what those switches do (when they should close).

also note that if the control bank resets and/or the target bank resets, then motor 4C switch is working.

since this is the 120V circuit, it's safer to check stuff without a jumper until you really need to use one. Easy things in this order are:

1] is the P relay being held powered? If no:

2] hold the O relay closed (push armature plate onto coil top with finger) and push the score motor a bit until the motor powers and the cams spin 120 degrees.

If the trip bank didn't reset, the O switch, P switch or a plug connection is the issue.

if the trip bank did reset, then the O relay is not powering when it should so find the O relay on the schem and see what makes it power.

assuming I'm not having a major brain fart, the trough switch is the one that closes as the ball is tossed over to the shooter, while the ball return switch is the one that closes when the ball lands in the hole at the bottom of the playfield?

if so, your P relay is operating correctly, but that doesn't prove the switch on it with the blue and brown wires along howardR's red line is actually closed/working when the P relay is unpowered.

looks like an O relay switch powers the score motor, so what happens if you close/push down the O relay armature plate onto the coil top when the game is reset (first ball waiting to be shot)?

what you are trying to find out is whether the problem is a switch along the red line, or the O relay is not powering when the ball drains. If the O relay is not powering, you need another red line from howardR in the O relay circuit.

Did you watch the switches opening and closing?

For a switch to work 3 things are necessary:
1) When open, there should be a small space between the contact points (duh)
2) When closing, the long blade's contact point should push the short blade's contact point enough to move the short blade
3) The contact points should be clean, which they usually will be if #2 is happening

the E relay switch is for resetting the target bank when you've gone over the outside rollovers or the "target bank sequence switch" closes.

the target bank is also supposed to reset when a ball drains without going over rollovers, which is what howard's circuit is doing.

which problem were you having?

if you've misadjusted the E relay switch so it's always closed, the target bank will reset any time the score motor runs ... e.g. hitting something for 500 points + bonus advance.

if you stick a piece of paper between the E relay contacts you adjusted and drain the ball between the flippers, the target bank should still reset. If it doesn't, you still have a problem.

does howard's circuit make sense to you in words? e.g. "when the ball lands in the return hole and before it's been kicked over to the shooter, the target bank will reset".

mapping that statement to the O relay/return hole switch, P relay/trough switch and the score motor turning is the goal.

live with it and waste a great opportunity to break something else?

the add player unit coil circuit is ugly ... if you decide to dig into it, you'll wind up understanding how pretty much everything works ... the score motor, motor sequence chart, player unit wipers and cams switches, etc.

you'll need to look at the manual, schem and the player unit cam switches to make sense of it, and keep in mind the game is a 2 player version of Big Indian, so I think the player unit behaves like you are playing 1 or 2 players on a 4 player game.

e.g. for a one player game, I'd verify the player unit is at reset when the first ball is sitting at the shooter, then goes to step 4 when the second ball is at the shooter. Figure out how it made those three steps and you'll have a better idea where to point the shotgun for dealing with an intermittent problem.

They're switches on the Player Unit. Here's the relevant extract from the last page of the Big Brave manual:

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