HELP NEEDED! Pulsacoil 3 overheating

Hi there.

I need some help as I am out of suggestions.

My pulsacoil 3 is overheating and the overheat button is popping out so I am having to pop it in every night. I have replaced the thermostat sensor as well as the thermostat rod. The LED on the board is flashing twice per second so looks normal.

What else could be the problem please? Funds are low so would really prefer not to have to get an engineer out.

Any help is appreciated. Please help asap!

Many thanks
Howard