Progress, maybe. Last place that I tried the paper test, because it was a bit of a pain to get the paper between the switches. The 1000 point, open gate target in the middle top of the pf. Blocked both switch contacts behind the pf target, and through 2 simulated by hand games running the score well over 100K, and then manually clicking the 1000 point relay (which had caused it to stick earlier in the night) to well over 100K points. Then playing 3 actual 2 player games. No relay sticking.
So, assuming the game isn't just playing with my head. The problem is somewhere in the gate pf target circuit. Interestingly though, had put paper in the gate side out lane switch, and in between the switches in the gate relay, which is under the pf near the gate. And in that case, relay still stuck.
So could it be as easy as the gate pf target switches adjusted to closely? Will try to open the gaps and see what happens.