We have a De Dietrich DOD 788X pyrolytic double oven. The main oven stopped heating a couple of weeks ago in Circulating heat mode (element at back of the oven heats in this mode) and on removing the element at the back we found that it had literally melted and bits of it were scattered on the bottom of the oven. We replaced the element and the oven worked for about a week and then stopped working (fan works but no heat). We thought it was probably a bad element and replaced it but again no heat. We swapped the temperature probe between the top and bottom oven to see if that was the cause but still no joy. We can get the elements on the top and bottom of the main over to work (using the combined heat mode), but the element at the back won’t work (circulating heat mode). The fan seems to be working OK in the main oven

The oven is 10 years old, is it worth repairing and what else could be causing the problem, a relay switch on the circuit board?