CREDA "Concept Solarplus" is tripping the house ECB?

Maker: CREDA
Model: 48347
Serial No: 67 1 00048

Fault(s?):
i) ALWAYS, whenever the Top Oven is switched ON it causes the house ECB to trip
ii) SOMETIMES, when either the Single or Double Grill is switched OFF it causes the house ECB to trip.

I believe that both of these failure-modes commenced at the same time and that they are therefore very very likely to be due to a single fault. What is that fault?

I am inclined to believe that the Top Oven heating element is shorting to its outer cover but I cannot see how this would lead to the second failure-mode. Does anyone out there have a copy of the circuit diagram that I could see? Or have you experienced the identical fault before and managed to repair it?

With thanks,

Ted.