My ~10yo 'van is based on a Fiat Ducato, like many others. For obvious reasons, it hasn't been used much lately
I recently took it out after not using it for 4-5 weeks, just so that it got a run. None of the instruments (speedo, rev counter, temp and fuel level) worked. They were all stuck hard on zero.
Long story short, I took it out (fairly easy, videos on YouTube) and got it fixed locally (£125 - a replacement is about £600 on Ebay). The guy who served me told me it was a common problem with Fiat Ducatos, especially motorhomes, that get laid up for a while. The motors inside seize up.
So, be warned, at least start up your Fiat Ducato occasionally, and preferably take it for a run.