Frequent frosting over

Question

I have a GE side-by-side GSS22WGMD that frosts over every couple of weeks. Usually the first sign is the water dispenser line freezing up/vegetable drawer contents freezing and the fridge side gets too warm. When I get to the freezer coils, they are totally iced over. I defrost it, it regulates the temp okay for another couple of weeks and then repeats the cycle. I've replaced the circuit board, which seemed to fix the problem for about 6 months, but now it's back to the same old frosting over cycle. Help!