Mschmidt I do agree with processhead that it could affect the airflow. When I make jerky in the smoker I leave a square in the middle of each screen about 6" x 6" to allow for proper airflow. Were your sticks taking up all the space on the racks? Unless they were jammed in there on each “row” then I wouldn’t say this was the main cause. Sticks are pretty thin and they should finish up quickly even without ideal air flow.
So, no fatting out and your thermometer is good. If you are going to continue doing this I would recommend that you get a prober thermometer that can be left in, as you said opening the door is setting you back significantly. Doesn’t have to be an expensive one at all, there are a few models out there in the $20 range.
What were your dampers at when you were at 175-185, you mentioned it in the leading up stages but not that.