Gulfstream is doing a strange thing. Lets me reset the game, ups ball count to 5 (or 3 after I changed it) and put the ball into the shoot lane. Play the ball, and when it drains, it drops the ball count light from 5->2 (or 3->1); on next drain, the ball count light goes off completely, but ejects the ball into play. If you drain this No-Light ball, the ball is not ejected, but the game isn't over (Game Over doesn't light) - if you trip targets on play field it'll score.

This game does add-a-ball if you hit certain targets, I was able to up the ball count to 7, draining from there proceeded correctly 7->6->5, then 3 then 1 then no light, no game over.

I've manual and copy of schematic; unfortunately it seems like many labels on the relays/discs are missing so I'm having trouble finding my way. The ball count disc is not in the backboard?

Ok, I figured out the ball count disc is indeed in the backboard. It seems like it had been worked on once upon a time; the clockwork gear would skip towards the end; I noticed the wound spring was a bit loose, I turned it a couple more times and that seems to have improved the ball count down behavior and setting game over correctly.

As a side note, unplug the game while doing this. The spring leg touched one of the relay leads and shorted, popping the 15AMP fuse. Dummy me. I've got friends who call me Captain Zzzt-Pop for a reason...