Smeg cooker smells like burning – what could cause this?

I’ve actually stopped using it now – but our roughly ten year old SUK62 (free standing dual fuel, double oven) cooker has begun to emit a rather strange and pungent odour when in use.

It takes a few minutes to warm up and then it starts to stink – not inside the oven, which smells like the food that’s cooking, but from the vent at the top.

I’ve disconnected the gas, isolated the mains at the wall and consumer unit (we had a rewire a year ago, when we moved in, and it has its own circuit) and taken the back plate off – all looks normal apart from some blackening round certain wiring blocks and so on, which I believe may be normal? The actual terminal block on the back plate looks fine inside, no melting etc.

It certainly smells like insulation or a plastic sort of smell – a bit like if I had left some cleaning product in the oven, except I haven’t, and the oven itself doesn’t smell when you open the door, even when it is on.

I’m just wondering what this might be being caused by as I’m torn between shelling out for a new cooker after 10 years of this one, which has been fairly trouble free, and getting it fixed (by a non Smeg agent as it’s no longer in warranty anyway).

I know parts are £££ (had to replace door glass after element went and repair chap leaned on the glass, because I forgot how to remove the door and was holding a new baby at the time) but is it likely to be something expensive? Also is it like a car and more and more things will go wrong from here on in?

Want to do the most sensible thing and I do have funds for a new.

Thanks in advance for any suggestions or thoughts.