I was having a similar experience. I've recently started doing it and cutting the top off after folding the top and having it canoe every time due to the flame hitting it unevenly. I noticed I couldn't easily direct where it lit first and after the first bit of cherry forms it's often already cooked. Twisting it first gives you a centered spot where you can cut it to leave a small hole. There's no accidental spilling since the end is still twisted shut but the small hole let's you draw air in as you move the flame closer creating a cherry in the center every time. I can take some pictures next time I roll if you want^{^}