you asked for a schematic with colored lines? OK! Hope you aren't looking on a small screen
for a win on card 3 in holes [20, 9, 21], no doubling, the sequence is:
1] orange. Wire 70 is connected to some coils and the bottom of CU 8 switch.
2] you've pushed the C button and the 3-4 search wipers spin around to position 41.
3] yellow. The yellow circuit path completes. The 3-4 search index coil is powered and stops the wipers at position 41. The top of the replay counter step-up coil is connected.
4] green. The 3-4 search index switch closes and connects the regular win relay. The search index coil is switched to power thru a resistor to reduce heat. The game is waiting for your double/nothing choice.
5] blue. You push the R button and the regular win relay powers. The replay cams index coils powered and the replay cams (under CU 7-10 switches) are released to spin. The alternate current path to CU 7 patch switch is closed. CU 10 switch is open most of the time while the replay cams turn, but a replay cams index switch keeps the yellow circuit closed.
6] purple. As the replay cams switch, CU 7 pulses the replay register to add credits. The cu 7 back switch also provides the redundant path for the high power solenoids (replay register and replay counter step-up) to prevent pitting of the replay counter printed circuit traces.
7] teal. CU 8 pulses at the same time the 4th credit is added to step up the replay counter.
8] red circles. If the replay counter has stepped off the active traces, the yellow circuit is broken. When the CU 7 back switch opens, the purple and blue circuits are open. The search index coil and replay cams index coil lose power. The search wipers are released.
9] win detect is inhibited until the replay cams spin around and lock home. That closes CU 10 again.
the only way to stick on the replay counter step-up coil is as you mentioned...the teal circuit needs to have a closed path to the orange.
since cards 1-2 work and the teal circuit is shared with them, the implication is there's something related to the 1-2 search wipers/contact plate that's providing a current path...hence the "stick paper under the wipers" test when the replay counter step-up coil is stuck on.
the usual problem is a slip ring wiper in the wrong groove on the 1-2 search wipers or the search wipers aren't locked in the correct position.
I thought you checked/fixed the locked position of the search wipers. If your pic in post 35 is where your 1-2 search wipers are locked, you're in trouble. You will be creating a circuit path thru the 1-2 search index coil/resistor and replay counter #1 step up coil that would likely be good enough to hold in the solenoid plunger.
usually the 1-2 search index coil would power at the same time as the 3-4 when the wipers are locked in the wrong place (finger on the B rivet), but it is dependent on the resistances of the coils.
I'm guessing there's no way anyone read this far. If you did and understood at least half of it, get a drink