Glow Worm 70 FF Boiler Fault?

I have a glow worm 70ff boiler. It keeps going out and the cold air blows out of the exhaust pipe.

If I reset the temp switch to off and turn back on, I can hear, electronic ignition fire a couple of times, then it ignites and all is working fine.

Just some days it doesnt catch or goes out .

Any ideas please.