Check the switches on the flipper mechs. There should be a switch on each that closes when the flippers are activated, that will scroll through the letters. They are likely not closing all the way, or check for corroded contacts or a broken wire.

Also, does your lane change work?

Sorry, you want to look on the actual flipper mechanism under the playfield. The "longer" switch is your EOS switch, the second switch in the stack is normally open and when the flipper is activated it closes, which triggers a lane change or the changing of letters.

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Does it work now? Inspect the left one for a broken switch or if it's not closing when the flipper activates.

I meant the right side after you solder, but I’ll take that as yes...i hope!

Awesome, check the left one for good contact/continuity.

Do they register in test mode? Check them for continuity when they are closed with a multimeter. If the wiring and switches are good we can go from there.