Bizarre Thetford N150 Fridge fault

Thetford N150 fridge. Working fine from Thu to Saturday last week on 240v and had been also fine on 12v. Suddenly found the fridge dead - no display, no interior light, contents warming up in fridge and frozen food cpt. No amount of pressing the on/off button or disconnecting mains, running on engine battery, etc., made any difference. Back home - have fiddled with anything and everything (which has only revealed that the expected and identified fuses in my 2007 Adria Izola M/H electrobloc 225 don't seem to have any connection to the fridge!). However, the thing has sprung back to life for no obvious reason. The shortfalls are that it is not seeing gas supply - which I've checked is ok, and more significantly, it won't switch off. It runs fine in manual and auto on 240v and 12v, switching between both ok, but does not see any gas supply (and I can't hear any sparking attempts) and will not shut down. I tried disconnecting and reconnecting the control pcb in the front panel, but still the same. Any thoughts, or should I just buy a new pcb and hope for the best (£65)?