I have cooked these without any problems for months. It did take me 3 months of practicing (almost every weekend) to get them right though.
Cook on a rack in the cooker at 250* for 2hrs. Wrap meat side down in large aluminum pans with butter/sugar mixture (I do not worry about the liquid being on the back when I start, but it does not cover the ribs in the mix when melted). Back in the cooker at 250* for 2hrs or until they are tender. Once they're wrapped, I check them every 20mins for tenderness. I rotate the pans, as needed, to ensure all 4 racks cook properly and evenly. IF they finish before my pull time, I put them into the cambro as is. If not, they get pulled from the liquid at 11:15, sauced, and back into the cooker to let the sauce set. Any that are in the cambro get sauced at this time as well. I continue to check tenderness even after sauced to make sure they don't run over. If they are close, they go back into the cambro and wait.
This process has worked beautifully for us for this season. In 6 competitions, all using ETs, we've had 5 rib calls (and the 6th competition was a bit of an anomaly).
Good luck!