My son has a PE Super 27 that was built in 1995. Interior of the box in great shape (bricks, baffle and rails). The insulation will have to be replaced. He is getting some kickback smoke when he opens the chamber after starting a fire. I can figure out why this is happening. Can anyone advise? Chimney and stove are clean. Prior to this stove he had my 1989 Super 27 and there was no kickback smoke.. Thank You..>Dave