On our Force 10 the thermocouples worked in the following way:
When sufficiently heated by a flame an
electrical current was sent down the tube from the thermocouple flame
sensor to an electromagnet at the knob assembly. The magnet holds the gas valve open. We found that the
electrical current was not passing to the electromagnet due to a loose connection at the back of the knob. The connecting nut can be slightly tightened to ensue a good connection. Be careful not to smash the small button inside which makes the actual connection (this applies to thermocouple devices with a copper tube that carries the current to the knob, newer stoves have a wire with a ring connector instead of the little button inside).
You also could have a faulty electromagnet. These are easily replaceable.
Since your oven fault occurs with both the
grill and the burner it implies that the problem is probably at the knob end of the system where one electromagnet controls both burners.
At least that is how mine works.
One other note: The flame
sensor works when there is a sufficient temperature difference. When the
stove top burners are on the whole
stove heats up and that temperature difference may not be enough, so the oven burners go out.
We have not
solved this last problem so we take the dangerous approach of holding the knob in with a knife pried behind the handle. (not recommended)