Hello Damian,
I don't think that it is just the latest generation of caravan fridges that cause problems, as I have a 5 year old Thetford, supplied from new, that has been changed once ( by Thetford) but still gives ongoing non predictable problems on gas. At one stage, in a moment of desperation, I asked the repair workshop whether I would be better changing it over to Dometic, and their response was that they are all as bad as each other, and are too complex. I don't recall ever having a problem with the old type, where you could see the flame through a tube in the fridge. Surely in this day and age you would think that these manufacturers can make a reliable 3 way fridge?? Ater all Norcold (Thetford) and Dometic ( Electrolux) are not without experience in production of white goods.