Ferolli 25 OV Intermittent Loud Banging

We have just had installed a Ferolli 25 OV boiler to replace out old condensing boiler. However it has developed a fault that the installer cant seem to fix!

a) Intermittently (every other day ish) it will run for about an hour and then start to Bang....and I mean Bang...sounds like loud gunfire....like something is expolding in it!
b) If you then turn it off and then on again....it will work fine until it does it again.

We have had the Ferolli engineer out. He says that there is no fault with the boiler. Must be something to do with the installation. He has suggested the following:
a) Debris in the gas pipes as we are on LPG. We had NO issue with the old boiler and seems too much of a conicidence that it has happened exactly at the same time to me!
b) Limescale - flush the system. We rang the installer and he said that he has already done that....and he is stumped!

The only other thing that happened at the same time is that he installed an extra radiator in the Kitchen...apart from that it was a straight take off the old boiler and replace with new!!!

Any ideas out there....as we are stuck with in the middle with a boiler that is obviously not functioning correctly.

Help!

We have same problem with our new boiler - bangs in the pipes. Bleeding the radiators several times seems to have helped significantly. The plumber also suggested it can be caused by incorrectly fitted thermostat valves on the rads or the ball cock in the feeder tank opening and closing from waves

Thanks Andyjrb.

The noise is coming directly out of the boiler....not the pipes. We also had a new radiator fitted with a thermo valve.

Sounds like that may have something to do with it.