we have a nine year old fireplace insert; and this past year we have had some problems cotroling the flame. It is very uneven even though we have removed the glass and removed the logs & vacumen the holes to make sure they are not blocked. We have tried adjusting the vents for air and still when it starts ups only half lights up and it takes 15 to 20 minutes before everything is lite. Is there possibly a problem beown the plate that holds the logs etc. gas line that might be plugged some how?