Pull the circuit board out, note where the connector pins are soldered to the circuit board, the solder breaks over time from connector vibration.

If you get a good set of readers or magnifying glass, you will see a slight black ring all the way around the solder joint that have failed.

This is the break and light arcing creating this black ring.

Toss a little flux and a dab of 60/40 rosin core solder and bump each one of these. 9 times out of 10, it fixes it.

Then secure the wire plugging into it from vibrating.

I have bookmarked your link too. Good source.