I bought a simple 18.2cuft top freezer (no ice maker) in January. I'm getting frost on things in the freezer (the doors stay shut tight) and freezer burn.
To check out the temperature over time, I placed some calibrated data loggers (small battery-powered devices that record temperature) in the freezer and 'fridge. I let them collect data over a weekend when I was away, so the doors were never opened. Attached is a jpeg of the temperature graphs over a 48-hour period. The data logger on the top shelf of the freezer was sitting on top of a carton of ice cream, so it was about an inch from the top of the freezer. The lower one sat on the floor of the freezer. Neither the freezer nor 'fridge was stuffed with food. There was room for air circulation.
I realize this is air temperature and not food temperature, but should the temperature swing that much? I figured the defrost cycle was shorter than that.
Any insight someone could give me as to whether this looks normal or not would be appreciated.

It's at the recommended setting, which was the middle of five possible settings. Think I should change it to the next warmer setting and try again?