Not sure this is relevant to your case. But every fridge that I ever had, including my current one which is however 14 years old (!!) had/has a similar problem to the freezer section of it. No matter what manufacturers claim, they always slowly and gradually accumulated ice in the freezer section, so that every once in a while (one year? Two years? Maybe more) you need to empty it, "defrost" it (often helping yourself with a hairdryer to speed up the process :D) and put all that can be saved back in, throw away all that can't be put back in.

No ice maker device involved or at all included in the fridge - as it usually happens in this part of the world where, for some weird reason, ppl don't like it/are not interested in it, and prefer to have more space in the regular fridge.

I always thought, and still think, that I was doing something "wrong" and there must be a way to prevent this, also because most fridges are, I believe, "no-frost" or whatever they call them. I never wanted to spend time to find out, as it normally takes such a long time to happen. But, it looks very similar to what happened to you.