I had this same problem of lots of air leaking in from somewhere else other than the obvious places, like the rope or front vent. I found that the paddle that covers the vent underneath the stove was flapping down at the back end and letting lots of air in. However, I wasn’t able to tighten that bolt any further - it was as tight as it could go. I found the solution was to remove that bolt and then bend the entire flat section of the metal paddle upwards so that when I put the bolt back on, the entirety of the metal paddle was pushed against the vent. It worked a treat and I can finally run my stove the way it’s supposed to function - yay!
