problem with my beko dv555?

I bought it second hand a few weeks ago, it's about one year old.
It has started acting funny recently, when i turn on the bottom fan assisted oven it makes a bump noise, which continues on and off, this is hard to explain, while making this strange noise the light flickers in the oven then the cookers turns itself off, it is wired correctly, any ideas what the problem is? replies appriciated.