STOVES OVEN possible thermostat problem?

[Nikki]

Hi
Why do things always happen together!!
My oven is now only producing a small flame at the back, normally when you adjust the control knob the flame will go up or down
No issue with the grill or the hob
It's the original one, so 22 years old and normally works a dream , never any issues, apart from occasionally needing to put a pin into the jet, I am presuming this could be gunging from some Lpg
The flame stays lit so not the thermocouple
I'm wondering if thermostat
Anyone any experience of these?
Any ideas greatly appreciated
Also any ideas of where to get one, I do have the model and serial number but can't seem to find any on the tinternet and have now got a headache ?

 

[Nikki]

Wow its not that dirty, the carpet is reflecting in the glass ?

 

[Corky1009]

Will be blocked jet, take 2 screws out of burner top and clean and if still not working the jet itself ( small brass in centre) will be blocked would need to remove and soak to remove dirt but don’t insert anything into it as you can alter the jet size.