I recently (2 weeks ago) and my second Defiant VC wood stove installed. It is the 8" oval connection, straight up venting through the ceiling. I have never experienced this before - but once I went through a few days of slow burn, I fired it up. I can SEE flames between the stove and the base of the flue. It is a very small opening, but you can see the flames. at one point I turned the stove way down (too fast) and smoke came out of the same location. My installer is telling me that is normal?? I have never had smoke escape, nor been able to see flames. I appreciate any feedback.