What is causing our AEG B4101-1-M oven to cut out after repair?

Oven overheated and cut out everything. After establishing that main oven thermostat was not clicking on and off as you turn RH knob round and back, decided this was cause of fault and replaced part. Worked fine and thought job well done. Next time my wife used the oven, it came on OK for approx 5 minutes then tripped the mains distribution board RCD. This now happens every time oven turned on - can be 5 minutes or 15 minutes, but any movement of the thermostat or main control knob (either!) causes tripping. I have double checked all spade type connections, and blue limiter that controls cooling fan is intact. No obvious signs of burning to the main control contacts
Having replaced faulty thermostat, what can be causing tripping?