I have smoked ribs two times over indirect heat on a charcoal grill. About 275* for 4.5 hrs, always came out great. Santa delivered a propane smoker. Couldn't wait to try it. Its directions advised to cook at 200* for 3.5-5 hrs. I smoked at 200*-210* for 5 hrs, they were anything but fall off the bone. My guests ate one rack, I put the other rack in oven at 325* for 45 minutes, then they were better, still not really tender. What went wrong? thanks in advance for your thoughts!