Per the suggestion to the question Samsung RF266 refrigerator not cooling - Fan making noise I completely defrosted the refrigerator. The issue went away for a few days, but re-surfaced again. So I decided to disassemble to refrigerator understand the root cause of the problem. Yes there is Ice build up. Here are some images.
As you see in the image below. There is a good amount of ice buildup.
What are any suggestion to try fixing the issue? How can one test to verify if the fan is still working.