zanussi duo ZHF 865X top oven trips?

i have a zanussi duo ZHF 865X and when i turn the knob for either the top oven or the grill knob it blows the house trip right away ,if i use the bottom oven its working fine ,ive seen on some spares sites theres a thermal overload in the roof of the top oven ,could this be the fault or is it something else? any help would be great