When I first received the machine the owner said that sometimes the game didn't start when you turned it on, it just kept cycling, and so he'd turn it off, then on and try the start button again.
What was actually happening though was that the player motor was moving SO SLOWLY that the startup cycle was taking far longer than a reasonable person should be expected to wait.
This created erroneous scoring issues as well: After ball 1 the player motor has to advance, but the ball is already in the shooter lane, so the player would shoot the ball, but the motor would be in player 2, 3 or 4 position as it tries to advance to player 1 ball 2.
All this because the player motor was spinning far slower than it should. I found this thread on MAACA where someone else had the same issue, and described the player motor as a bit difficult to reassemble. Due to the implied complexity (the guy in the thread repairs BINGO machines, so for him to say it was a challenge is intimidating...) I had someone in to help me open up the motor and clean it up.
After opening and cleaning the drive section, the motor goes much faster, and the startup delay and scoring issues are gone! The motor was always especially slow when turning it on a first time, but now it is far better. Odd to think of a pinball machine "warming up", but that is exactly what this one was doing. But before it never even approached a reasonable rotation speed, even when used heavily.
That same thread also contained another member's insights in to my scoring issue. Behold the scoring schematics section:
The CE / ML / DM / CM solenoids are the relays that trigger the score reel solenoids as well as the digital chime sounds.
The issue was the make/break relay P. P, R and T make/break to determine if the pop bumpers are 1000 or 10000. I had never before found a make/break relay that was gummed up and connecting on both sides, but this one was. This also explains the intermittency of the issue, since the relay wasn't always engaged. But when on, both sides of the P relay were connecting. That is why when I manually trigger the DM relay, the ML would also fire.
Here is a schematic detail of what was firing:
This was also manifesting as another symptom: When the 2 solenoids were advancing at the same time, sometimes the power wasn't strong enough to clear them to their next position. AND, if the 10k was rolling over from 9 to zero, then 100k reel would advance as well and there certain wasn't enough power enough to advance all THREE reels properly.
This locked on the relays, and would cause the sustained squeal of the digital chime. And this was the first and most major problem that the owner was complaining about.
Oh and we also installed a new power plug to replace the busted and frayed one that was causing the underside of the playfield to be hot/live. Safety first!