We have a propane Majestic FP with a direct venting system and connected to the mains with a switch on the wall. This unit is about 10 years old and we had it installed by the dealer.This is not our main heating source and only use it first thing in the morning (Winter)when first out of bed. Over the years we've had it serviced and it has worked with no problems until recently. When I hit the switch to ignite it, 80% of the time the whole burner will not light and I get a mini explosion, then the unit will light and run as normal, the other 20% of the time it will light as normal with no problem. We've had the servicemen (different guys) in twice to see if they can find the problem and during their visits the unit worked as normal, so they couldn't tell me the problem. They tell me it could be this or it could be that and it is expensive to get these guys in all the time with no positive conclusion.

After reading some posts I think a lot of you who write here are quite knowledgable with FP and I would like to have your opinions as to what might be my problem.

Thanks in advance!!