Once you're satisfied that the Player unit is working mechanically, here's the circuit that advances it during a 1 player game.

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PU does do that stuff, TT. Make sure all the rivets are shiny clean and that those springy little connectors are making good contact. The switches in the back of it that are referred to in Howard's diagram are a pita to clean and adjust because they've got lateral connections soldered in, but you have to make do. While you're at it, take a good look at the switches on each score reel for cleanliness and good contact. Hopefully you don't need to get into the motor switches, but if the above doesn't work you will have to check them out.

Regarding the scoring issue...do the L,M or N relays operate when you activate a scoring playfield switch?

L,M,N are in the head (1000, 100 and 10 point relays)

Hi TaterTot
faults of the kind "not every time" are specially annoying - tricky to detect. The stepping through players / balls in a Gottlieb pin is complicated - the mechanism must cover "ONE-Player-Game" - the next game might be a "THREE-Player-Game" - then an 1- or -4 or -2 or -3 Game. The mechanism must handle every kind of a game. The simplest form is an FOUR-Player-Game.

Please play many FOUR-Player-Games - big question: DOES Your "sometimes" fault show up ? Write about.
IF (if, if) "NEVER shows up in a FOUR-Player-Game": Play many THREE-Player-Games - big question: DOES Your "sometimes" fault show up ? Write about.
IF (if, if) "NEVER shows up in a THREE-Player-Game": Play many TWO-Player-Games - big question: DOES Your "sometimes" fault show up ? Write about.
IF (if, if) "NEVER shows up in a TWO-Player-Game": Play many ONE-Player-Games and write about.

Theory to come - but it helps me "writing" when I know about the "written above". Greetings Rolf

Hi TaterTot
why did I ask You "please play many FOUR-Player-Games ..." (see post-11) ? I took HowardR 's picture from post-4 and added some drawings - see the JPG - when we start for the second Player: The PB2-Relay (for second player) sitting in the Control-Bank plunges and stays (through the hole game) plunged --- switch (lightblue-3*) "PB2" will be open through the hole game.
When we start for the third Player: The PB3-Relay (for third player) sitting in the Control-Bank plunges and stays (through the hole game) plunged --- switch (darkblue-4*) "PB3" will be open through the hole game.
When we start for the fourth Player: The PB4-Relay (for fourth player) sitting in the Control-Bank plunges and stays (through the hole game) plunged --- switch (brown-5*) "PB4" will be open through the hole game.
Therefore: In a running "Jungle" NEVER current can flow through "lightblue / darkblue / brown" wires.
IF (if, if) You play many FOUR-Player-Games and the pin sometimes makes more than one step: Fault must be on the "lightblue-3*, dark-blue-4*, brown-5*" switches.
IF (if, if) You play many FOUR-Player-Games and the pin sometimes does not step: Fault must be in the wiring and switches along "red - orange - red" wiring (do not forget to make some points on every ball).

SteveFury made an excellent topic - https://pinside.com/pinball/forum/topic/em-pinball-circuits-basics-to-not-so-basic --- look at the first animated GIF in post-54 - a four-player-game --- ALWAYS just one step (along my (JPG) "red - orange - red" wiring).

In SteveFury's topic, post-54 the second animated GIF shows the stepping in a ONE-Player-Game --- his switches below the words "CAM 1, CAM 2, CAM 3, CAM 4" act synchronous with (my JPG) "not shown in the snippet - lightblue-3% - darkblue-4%, brown-5%" Switches. Greetings Rolf

P.S.: The "written above" is stepping in a FOUR-Player GOTTLIEB pin --- Williams and Bally 4-player-pins have an completely different way to step through the players / balls.

0Jungle-pinside-pic-Work-01 (resized).jpg