UPDATE....
I've rebuilt and cleaned all of the score reels.
Here's what's (still) happening.
Upon starting a game, Player 1 and 2 reels now reset to zero, Players 3 and 4 don't move. Player 1-2 reset relay keeps pulsing with the score motor. If I manually reset players 3 and 4 to zero, the player 1-2 reset relay stops pulsing and the start sequence appears to complete. That's when the 10pt relay locks on.
I've checked the 10pt switches, pop bumper relays, pulse relay and advance unit. Is it time to start desoldering switches and relays?
I've also found some hacks. One of the jones plugs (upper left one) in the back box had all of the wires cut and spliced back on, but they appear to be correct. One pop bumper coil had electrical tape around it and one blade on its EOS has char marks.
Thx.