i no longer have my Pinbot but the last thing i did before it left was to fix a dead top pop bumper.
Not sure which switch the game was telling you to adjust on startup - there is switch that the spoon closes when the ball hits the skirt and the scoring switch that closes when the coil pulls in. My guess is that switch hasn't been seen by the MPU in a while (since pop bumper is not firing) and when you were cleaning you manually closed it which will for the time being get rid of that message.
Anyway - this coil is part of the special solenoid section on the MPU (top corner near the relay). Q78 and Q79 are the associated drive and pre-drive transistors, and further upstream are some resistors (not likely bad) and a Zener diode at ZR-7. U50 is a 7402 chip that circuit. I am no expert but learned a lot from Grumpy which is detailed in the link below. Perhaps it can help you as well.