Pork Butt Question

I cooked 6 pork butts over two cooks in my Akorn Kamado. Each cook took just over 7.5 hours @ 250 degrees. I cooked three on each cook. I prepped all six the night before. The first three were just as expected. The second three were a bit tough and not as juicy. The only difference was the first three were at a temp of 42 degrees when it went on the smoker and the pit temp was 250. I pulled the butts after 4 hours and wrapped them. I then pulled the butts when the reached 195. The second three I had laid out and they were at a temp of 54 degrees when they went on the smoker. I wrapped them after 4 hours and again pulled them at 195 degrees.my question is can the second batch going on at a higher start temp cause them to cook different. I have never had this happen before.

The second set is the ones that were slightly tough. I also use a BBQ guru digi q pit/meat control system. The second set sat out for about 2.5 hours were the first set only sat out about 30 minutes. The bones pulled from all 6 quite easily. I have cooked over 40 butts and never had this happen. I was disappointed in the second set.