My 91 year old regular does the same with a Compaq.

Stacked thighs means steam trapped between them. No airflow, no crisp. I do 6 wings max in my basket, single layer, flip halfway, and they come out perfect every time. Filling it to the top is just steaming your food at that point.

Two miles each way sounds small but it clearly adds up over a month. Good on you for keeping it going instead of giving up after a week like most people do. Short trips are the easiest to swap out since you barely notice the time.