This may be a long shot, but check the coil on the "P" Relay. It's the relay right behind the Total Play Meter. The P relay has just (1) "A" contact.

The correct coil for the P relay is a R-487 (R20-2).

I just got my first Pin, also a Gigi. I'm missing a relay so I was going over the schematic, trying to reverse engineer what I'm missing.

The P coil is in series with the 14 Interlock Relays (1Y-7Y, 1R-7R). Because P is in series with the other coils, it needs to have very low resistance. The R20-2 is just 2.0 ohms.

On my machine, the P coil is wrong. It's a R20-4 (15 ohms). I haven't powered up my machine, but I think I'd have similar problems. With the P coil being a R20-4 (instead of the correct R20-2), there will be less current flowing through the P coil and thus all the other Interlock Relay coils. This will mean the Interlock Relays may not have enough current to transition when the bumper's switches are activated.

This sounds like the type of problem you're having.

I restored two Gigi's in the last year, and both took a lot of fidgeting with the seven bumper interlock relays under the playfield before the bumpers would switch properly. In my case, cleaning the relay plates really well with alcohol, then novus 2 (which seems to reduce friction on metal) made a huge difference. Still, I had a couple of bumpers that wouldn't "alternate" reliably. Adjusting the metal "tab" on the relay to limit the amount of overlap between the two plates fixed that problem. Before I posted this I play tested a game and scored a couple of advances - every bumper hit registered properly during the game. You're right, Gigi is tough enough to beat, but about impossible if the bumpers aren't registering hits properly. Great game, though!

gigi L 053.JPG

That’s one nasty looking pinny you boys own, hate 2” flippers.

http://www.ipdb.org/showpic.pl?id=1003&picno=23244