Flew/chimney needs to maintain 300-600 degrees for smoke to exhaust out of your wood stove. Your massive chimney is 3 stories high..Its robbing all the heat needed and stalling out the smoke ..With a cold flew its going to take the least path of resistance and with a 14x28x36 firebox with the 6" flew mounted on the rear with 90s on it and a load door almost the size of the box?..I'm not sure what to tell you.
