Seven months of hot breath and you never noticed your glasses fogging up?

Had a similar thing with rats a few years back when I kept a small colony for snake food. What finally worked for me was going around with a cheap tube of caulk and a roll of steel wool and stuffing every gap I could find, even the ones that looked too small to matter. Mice can squeeze through a hole the size of a dime, so if you can see daylight or feel a draft, they can get out. The live traps are good but you have to check them twice a day or the mice get stressed and start dying off on you. Also keep the food in a sealed bin they can't chew through, because a hungry mouse will chew a new hole faster than you can patch the old one. Sounds like you already learned the hard way, but patching before you restock is the way to go.

The real issue is moisture, not temp. When you go straight from frozen, the ice crystals on the surface melt and turn to steam, which basically steams the skin instead of frying it. That steam keeps the skin from ever getting dry enough to crisp up, no matter how long you cook it. Thawing lets that surface moisture drain off first, so the air fryer is actually doing its job instead of fighting a wet coating.