Chaffoteux Maury MX2 30FF - will work for about 20 mins and then stop?

Hi

I have a Chaffoteux Maury MX2 30FF, this will work for about 20 mins to 30 mins and then stop with the error "No Flame Detection". I then have to leave this off for about 20 mins and then it will work again.

I have read that these seem to have issues with the PCB, but as this will work and then seem to "warm up" and then pack in, does anyone know of anything that this could be.

I don't want to fork out on a PCB when it could be something more simple.

Many thanks