I had this problem on my old caravan part exchanged c/van for a Lunar Solar but did tell the dealer and he checked it and suggested it required cleaning or a new gas module, I would get it sorted or you'll likely blow out the side of the van.
Carver I believe were taken over by Truma.
Try them. www.Trumauk.com ask them what they think it could be or an honest caravan repair shop thats near you.
bob
September 2010