Baumatic BWDI126N Dryer Stat intermitent O/C

I had a call to the above Baumatic washer/Dyer as the dryer was not heating.
The overheat thermostat was open circuit so I reset it.
The fan was clear and running OK.’
The NTC checked out OK.
No obvious problem with the wiring loom.
No insulation faults.
Inlet valves were OK.
I advised the customer about stopping the dryer mid cycle.

The customer has called to say that it’s stopped heating again. He has used the dryer about twelve times and worked perfectly until now and confirmed he hasn’t stopped the machine mid drying.

Any suggestions how to proceed with this fault?