I am having some issues with my 4 year old Lopi Leyden. Had combustor and bypass plate replaced by dealer before this season (bypass clip and gasket warped, repair man said combustor was "shot"). Stove worked fine until recently. Now when closing the stove down for an overnight burn (bypass closed and air flow knob pushed all the way in) stove appears to not get ANY air. Small puffs of smoke escape from under lid. House smells of smoke overnight. Have had to leave bypass plate open slightly. Any thoughts?