I verified chimney and cap are good to go, no issues there. To answer a previous question, the amount of ash from last year when I cleaned was fairly small - the stove is amazingly efficient. I just reinstalled the cat with a new gasket. So we’ll see what happens, but my plan is to just deal with it for the rest of the season and go to double wall pipe sometime before next season. I don’t think there’s anything left to troubleshoot/do other than blame the single wall for weak draft if the smoking happens again.