We had an issue with Our Samsung fridge that was similar. Our freezer would be fine, no frozen coils, but the fridge would not cool lower than 47F. I would "reset" the fridge (unplug) for 15 mins then start again and things would be fine for 3 days then go back. I checked the fan, just fine; the damper, just fine; but replaced both of them for the fun of it.. It came down to replacing and relocating the fridge temp sensors . After I did this, no more issues.
Samsung could not figure it out. No one within 100 miles of me would touch the fridge. Samsung sent me the engineering documents on the fridge and told me good luck. The fridge is only 2 years old.