Smeg pyro oven overheating

Hi all.
Thanks for your help in advance.

I have a Smeg oven FP610SV.
It all works perfectly for cooking food, however, recently when setting to Eco Pyro to clean, the oven overheats to the point where I am unable to touch the control panel, and then the power cuts out. (Does not trip the RCD)
I suspect that this could be a simple thermostat that needs replacing, but there seem to be quite a few thermostats and cut out switches available for this model.
I am quite capable of replacing any parts, so I don’t fancy paying £150 for diagnosis and then double the price for parts!
If anyone can point me in the right direction as to which part may be causing this problem I would be very grateful.

I also have an error code (err4) but I am aware that this is the door latch mechanism which I will be replacing also (unless advised otherwise by you helpful people)
thanks all.
Adam