Not sure if anyone has written about this topic before on these forums, but I wanted to share something I found in my recent inspections and maintenance on my newly-acquired used Giotto. I discovered that several of the plastic protectors covering electrical connectors inside the machine were quite badly discoloured. Most were normal - ie. pale amber colour or off-white (those away from the boiler heat). But at least four were a dark brown colour, esp, at the bottom where the actual female spade connector fits on the male terminal. You can see this in the following picture:
Turns out that this discolouration was actually an indicator of the real problem, which in my case was overheating connections caused by loose connectors. To check this, I wiggled all the spade connectors in the machine, and sure enough, those with the dark brown discolouration were loose, and those with normal colour were nice and tight. For those not familiar with electrical matters (I'm no expert, but I know the basics), when current flows through a poor connection, it meets resistance, and the resistance creates heat. Hence the overheating at the connector.
For most of the loose connections that I found, it was simply a matter of the compression arms or wings (for lack of a better term) on the female spade connector having become loosened over time. But in one instance (see photo below) there was also corrosion on the male terminal.
(Sorry for the poor picture quality - couldn't get my camera to focus on the foreground, but you get the idea)
The fix for this is fortunately easy. In my case, I was able to slide the plastic protectors off the spade lugs and gently squeeze the arms tighter with a pair of pliers. This tightened their grip on the male terminal - ie. it improved the connection by increasing the compression on the terminal. Several of the plastic sleeves were very brittle from the heat, and just crumbled when I pressed on them (I will replace these soon). An alternative would be to simply snip off the wire at the spade lug, strip bare some fresh wire and crimp new connectors on, but you would need good crimping pliers. You would probably only want to do this if the lug is badly corroded. If there is no corrosion, squeezing the connector is easier.
For the corroded male terminal in the photo above, I cleaned the connector by gently rubbing with fine steel wool and emery paper. It polished up nicely and all the crud was gone, leaving a nice shiny terminal.
After tightening all the loose spade lugs, they fit on their terminals as tightly as the rest of the connectors. I now have confidence that the connections are secure and that I won't have reliability problems from this source. I'll check on them periodically whenever I open up the machine for maintenance.
For anyone with a machine a few years old, it would probably be a good idea to check for this next time you open up the machine. Hope this helps.