I am going to go down a different path in my search for a solution.
I do a LOT of ribs some racks are better than others however, if a rack looks pretty good raw generally it will be good smoked.
I agree Sam's, Costco, and Restaurant Depot have massive buying power, but so does Sysco and I have seen them slip some crap product into the supply chain, you can get average meat anywhere. If you feel like your had good meat then it was likely good meat.
turned the temp knob halfway between 225-250. I was aiming for 235.
Let her run outside for 5 hours at that temp. Never opened her up and wasn't regulating the inside temps in the smoker nor the meat.
235 is not hard to find if you look close, also it is better to be a little lower than your target temp than higher. You mentioned you didn't monitor box temp, no big deal I never do. I think your main problem is running 5 hours without checking your progress. My #3 does whole racks to MY preference of tender in 3 hours and 45 minutes to 4 hours 15 minutes but we all agree my unit runs a little hot. They only way I learned how much time i need was by experimenting.
I opened that thing up and checked at 3.5, 4, & 4.5 hours for four of five smokes until I developed my routine. Now I just chuck the meat in, set the dial and come back in 3.75 hours.
Another variable you face is cutting your racks to fit the #2. This reduces mass and changes how they absorb heat. If you follow a post from a guy that loads his #3 to half capacity with whole racks then you try to duplicate his time and temp with your #2 and 2 slabs you will get very different results. This is not a problem just something else to be aware of.
Keep smoking it will all work out, don't be afraid to check progress until your used to it. I realize "If your looking your not cooking" but you can always smoke it longer you can't undue overcooking.
