Faulty bottom element on SCP160X?

I have a very strange element problem. Whatever function is chosen the grill & bottom elements come on & the temperature & end cooking result is fine. It appears that the rear element is not working & the grill can't work independently. Any ideas? It does still cook things but not using the functions that I would prefer.

I have a matching multifunction microwave that has been a nightmare from the off, it has had, a shattered door, replacement computer control panel (at Smegs expense after kicking up merry hell) a grill hook, light bulb, replaced microwave fan, an engineer to work out why it wouldn't work at all & found things were loose. Erratic behaviour at end time, loosing clock. Erratic fan 2nd time round. (on so called new computer board)
These were bought in Jan 2009. How I wish I had researched better.