If the player unit always advances when you manually actuate the P relay, then the problem may be that the P relay is not getting energized by the trough switch.

Check all the N.C. switches on the extra ball ("same player shoots again") relay. It's fairly common on Gottlieb games of this era to have a switch on the extra ball relay that opens to disable the P relay when the player has won an extra ball. If this switch is not making good contact, you'll get the intermittent problem you describe.

- TimMe

I am having the same problem on my 2 player fire queen, sometimes it advances but mostly stuck on ball 1 so I decided to shotgun file all the switches. Don't use a flexstone it leaves a non conductive silicate dust on the pads and you will have to clean it again with alcohol just use a steel file. My gut was to go to the eject hole relay and clean all the points, I noticed that when the "N" relay (hundreds) in the backbox was actuated the player unit would advance. I'm bringing her back from 30+ years of cold storage, oxidation city!