There are 4 blue relays in the unit that has solder points that will crack over time.
It´s fairly "easy" to re-solder them and viola, it´s OK again.
open the cover (unscrew and take of the hood) and locate the 4 blue relays.
Unscrew and remove the bottom service plate and locate the soldering points for the 4 relays.
Each relay has 6 solderings, 4 in one "groop" and 2 in one "groop" look especially at the "2-groop" these are the ones most likely to crack over time ( for me 12 years or so).
Re- solder. Best of luck //Ronnie Stockholm