Theres been a few issues on here lately with solenoid potential issues, i wonder if once the weather turns wet then cold the solenoid gets sticky or the vent filter blinds.
Your right on issues on fiat especially stilos.
On my jtdm the solenoid is sitting on the lower member same height as radiator bottom , alongside the bottom of the air box, it was a fit fix later to move them up and bolt alongside the battery.
When i did fmic i cut a piece out of front to clear pipework but made a good job of patching hole and sealing it for this very reason.
Ive left mine where it is as always looks clean and dry under there when i change air filter.
Im sure ive seen threads on stripping and lubing valve but may need epoxy to rebuild.
Im sure a squirt of wd40 into ports and clean and dry vent filter wouldnt do any harm, if your thinking of changing it anyway.
You may need some vac pipe off ebay also as pipe seems to age harden /split
I think its inner dia 3mm or 4mm silicone vac pipe thats recomended,
I have a meter of both waiting for that day when i need to do mine.