I was given a Kenmore Model 215O1, 5.0 cu. ft. capacity, upright freezer used in 2017. It has 2 shelves that both appear to have coolant being circulated through them. It has been in service until a few days ago when I emptied it to manually defrost the ice build up. I noticed then that only the upper of the two shelves had any ice build up. The lower shelf was cold to the touch but no ice. I went ahead and defrosted and re-started the unit. Nothing perishable inside it yet - only blue ice blocks. After running this way for a couple days, I can see frost forming on the upper shelf only. See the two red boxes in this photo. This is consistent with pre-defrosting but is disconcerting to me. Is this to be expected? If not, what - if anything - can be done? Thanks!