I would say that the chance of you being right on the cause of this is about 99% true.

The ice on the bottom of the freezer is crystal clear, not hoarfrost as would be the case if it were humidity condensing bit by bit. It is extremely likely that it is liquid water from the defrost system running down to the bottom and then freezing.

Unfortunately I can't do anything about it for a while. We just returned from a massive ($11,000 pesos) Costco grocery trip, stocking up for the next stage of the lock down, and other than where that block of ice is sitting, there is not 10 cubic inches of space open in that freezer (I learned from experience that anything placed on that ice becomes in that ice PDQ), and the "main" refrigerator/freezer in the kitchen is similarly encumbered. Once we eat enough of the food, I'll be able to transfer the remainder to the kitchen, get out the hair dryer and the tools and have a look.

Thank you very much for those links.

tanstaafl.