I had something similar with our side-by-side when we rented a few years back. These days freezers do auto-defrost cycles. I the case of my freezer there was a drain tube that would get clogged. Every few months we'd notice some water on the floor, and that was my signal. I would hammer out as much ice as possible, and then use a syringe to squirt hot water into the drainage hole to melt the ice in there.

Why this occurs I don't know, maybe it is just not sitting at the right angle...