Zanussi D/w Zsf6161 not heating 6 flashes

Have a Zanussi dishwasher here in the workshop. Its heating intermitently, some washes it heat and others it wont. Did the service test i60 is the fault .
The possible causes are heating element faulty, thermostats faulty ( as it does heat im ruling this out) so what im left with possible causes is the ntc sensor, wash pump faulty or circuit board faulty.

Any ideas??