My 2005 Bailey Ranger 470/4 has a large front window. The 2 parts of the window are expanding away from each other, caused apparentaly by my keeping the silver blind closed and the suns rays feflecting against it and heating up the window. The mechanic has said that it is 'blown' and will need a new window costing about £1,000. Is this right. What would happen if I remove the bung on the inside window and let the gas escape.