Frost Free but getting a lot of ice built up inside, main components check out

Fred, it’s actually very possible that’s your issue. Especially on these freezer units when you may not be in and out of them very often, even a little bit of constant warm air getting inside will cause serious problems over time. I’d definitely suggest getting the gasket replaced, it is a bit on the pricey side, but will keep that unit in perfect working order for quite some time more I’d guess. I’ll link it here for you. Part# is 4357142.