AEG B4140-1-W oven.

AEG B4140-1-W single pyro oven. PNC:- 944181741. Serial no:- 32833036.

This oven had a blown fan element. Replaced the element and switched on. The fan oven starts up, the element starts to get hot, then the pre-heat lamp goes out after about 30 seconds. Turn the thermostat knob higher, and the lamp will go out again 30 seconds later. The oven is nowhere near the dial temperature.
On further inspection, the PCB had fallen out of its holder on the underside of the lid of the machine and was laying on the metal body. No sign of burns or pop marks. Solder joints all OK. Put it back in the holder and tested it again. No difference.
I am assuming the PCB is faulty as the thermostat control is wired directly to the PCB. Could the sensor probe in the back of the oven be at fault? Does the PCB control the thermostat function as well as the pyroclean feature?
The PCB is costly, so any help would be appreciated!!

Thanks,

Steve.