ok, playing around with the game… seems like the scoring for the single eject goes like this:
Unlit, pays 10k
Right inlane will light the next level, which will flash. Depending on the machine settings, this could be untimed, or have a timeout associated (could be as short as 1 second).
You make the eject, it will award the flashing value, which will then light solid.
Subsequent shots to the eject will only score the 10k again, NOT the lit solid value. (confusing!)
Making the right inlane while a lamp is flashing on the eject hole will NOT advance it.
Making the right inlane which a lamp is solid should flash the next level, subject to the timer/rules above.
There is a flag in the code which I think concerns if you have already collected an extra ball/extra ball settings on the machine - this is the only way the game will avoid lighting the next level. The flashing code will always run after hitting the inlane.
It’s certainly very strange behavior, and I’m not surprised, really, since Bill Pfutenreuter was the programmer… he certainly was a bit outside the norm when programming. Not sure what they were doing setting the flags, they aren’t set/cleared many places in the code. But it does appear to hinge on those couple of flags… one is probably a flag that you are at your maximum extra balls already or they’re turned off, and the other is probably a flag that you already lit it for extra ball once this ball, so don’t light it again.
The code is certainly not straightforward… I would love to get a peek at the original source with the comments in there.
To sum up, I guess the answer as to why sometimes it flashes and sometimes it doesn’t, is that something is affecting those 2 flags in the advance code. Not sure what that something is yet, although for sure one is the ball start routine… it sets one flag and clears the other.
To complicate things, the eject hole timer is also something that is on the auto adjustments, so there is data in there for that as well.