AEG cooker U3100 – lower oven not working

Hi Am new to this site

I have been reading some of the problems that people are having with the AEG U3100-4-M oven, bottom oven not working but fan and light running. A friend of mine has had this and I have called around to help. It takes the RCD out. Do you know the solution to this? It appears to be the element, however, with this reoccuring so often and on new elements after only a couple of weeks on other peoples ovens is there a deeper seated problem.

Fan works clock works light works. Just no heat.
Prior to this my friend tells me that the oven would stop and then work again. Is there a over heat stat and could this be faulty or is it just the element?

Thank you in anticipation of your help?