Sorry for late reply. Split board. We have an rcd protecting the left hand circuits. No rcd on right which is where oven is. It is on it’s own circuit.. Electrician checked all the neutral lines and say all wired correctly. Chief Oven guy came today but also confused. Seems to be when cooling fan goes off whilst cooking (as opposed to going on), and when oven cooling after use and cooling fan just stops it also turns the rcd off. He is also very confused but is going to replace the thermostat safety cutout…still does not explain the rcd problem.. It is a fan oven.