The Multiball issue sounds like your trough boards are failing, very common. You can try to unplug and reseat them to see if that helps, but they are cheap so maybe replace them if that doesn’t work. They tend to work intermittently when they start to go bad as the transmitter will flicker at times with vibration.

Modes start with a shot to the ring. If your mode is starting that sounds like a switch/opto issue at the spinner or inside the ring. Put game in test mode and see what’s active. Roll a ball through the ring and make sure everything registers properly.

Do all of the switches along the ball lock work? Use a ball to test.

Seems like the game is losing track of the balls. Are the balls magnetized by any chance? Is there an issue with the shooter lane switch? I’m not sure what’s going on, just trying to think of things to rule out.

Yes, both lights should be on. You can try to resolder the transmitter, but I’ve had little luck with that and for $8, just bought new ones. Glad you got it going.