Hello guys,
I am new to pinside. I completely restored a Gottlieb Orbit over the past weeks as my first encounter with a pinball machine ever. You forums really helped me with a lot of issues.
The restoration is complete now. Me and my friends played like 10 test games, everything worked very well. We put the glass panel on and moved the machine to it's dedicated place and played like 5 games (3 players) without any issues when all of a sudden the ball counter did not advance anymore. It was stuck on ball one no matter what. During restoration I rebuilt every mechanical component (not all of the relays, only the ones I had issues with) but everything that is rotating, player unit works pretty well, all contacts are good, moves freely. During reset it switches through the players.
I already tried to check the switch in the ball output lane, it is also making good contact.

Do you guys have ideas on where to start digging? I am a mechatronics engineer and I understand the basic idea of the machines components but I am not completely confident in reading the schematics. I understand parts of it but not the whole thing. I have them and can post pictures if you tell me the area you need to see.

Thanks for your help.

Nevermind, found the error. The P-Relay for player advance did not get energized, just a bad soldering point.