delonghi dfs 903 - gremlins in oven settings!?

Weird one. Certain oven settings don't work. With the lamp as setting 1, going clockwise;
1. Lamp
2. Top & Bottom element heat.
3. Top element heats
4. neither heats - oven cold
5. neither heats - oven cold
6. Top element heats
7. neither heats - oven cold
8. Top & Bottom element heat.
As you can see, nothing wrong with the elements, it's just become impossible to have only the bottom element on without the grill, making it impossible to cook anything without burning the top of it! Unfortunatly lost manual as well, so unsure how to get in behind the clock, or get the top off, although I managed to get the back of it off this evening, but unable to get in any deeper!

Any help would be gratefully welcome, as unsure what part is broken, and how to get in to find out.

Thanks,

Jon