Why does the freezer temperature sometimes go up to 40 degrees?

I just had a new GTE16DTHWW refrigerator installed 8 days ago. This is a frost-free refrigerator with a top freezer. I have a thermometer in the freezer and the temperature always goes up to about five degrees before the fridge kicks back on and it cools down again. Some ice crystals and condensation accumulate in the freezer while the fridge isn't running. Twice I've noticed that the temperature in the freezer rises to 40 degrees before the fridge starts running again and brings the temperature back down. This model has one temperature control knob for both the fridge and freezer and I have it set to the coldest setting. My fridge section almost always stays at 40 or below but it rises to 45-ish at the same time that the temperature in the freezer rises to 40 degrees. During those two times when the freezer temperature rose to 40 degrees I noticed that the fridge was making a kind of buzzing or humming noise with an occasional hitch or glitch. It was like "Bzzzt, bzzzt, bzzzt, bzzzt, bzzzt, glitch, glitch, bzzzt, bzzzt" and so on.
I just checked my freezer while the fridge was running and the air coming from the back of the freezer compartment was somewhere between cool and cold but wasn't ice cold. After the fridge shut off I checked the freezer temperature and it's still at 5 degrees. I know next to nothing about appliances. Is this normal behavior for a fridge with a top freezer or is something wrong?

Edited to add: GE recommends that the freezer be kept at least 3/4 full. Mine is currently about 2/3 full. I don't know how much that might affect the temperature if at all.