How can I stop the burner going out when I turn the oven down?

Light oven normally by turning regulator knob to 9 then pressing in to ignite. According to instructions knob can then be turned to the correct setting, i.e. 4. After a few minutes the burner goes out and starts 'ticking'. I then re-ignite by pressing reg. knob again. The same thing happens over and over no matter what setting is chosen, except the high numbers 8,9. I've been told it's a thermocouple or sensor, but I'd like to what other people think. The oven is a STOVES built under oven, type 700GDOMK2BLK MODEL NO. 444440090 it's 16mths. old