Diplomat Electric Oven keeps Cutting Out?

I have a Diplomat ADP 4890 double electric oven. The top oven seems to be working fine but the bottom oven keeps cutting out during cooking (both in convential & fan modes) and will only work again when cool. Should the cooling fan service both ovens (I can hear it running when using the top oven but not when only using the bottom). Any help greatly appreciated. Cheers