Samsung SR-S2028cvw fridge section frezing up

Hi
I have a samsung SR-S2028CVW which every 6-8 weeks the fridge section fan starts to catch on ice build up, I have to take the false back off the fridge section and manually defrost the area.
Any clues and does anyone have a service manual they could email me at refrig@dship.net.
Many thanks

HI,
Ice build up have several reason:
1. probably fridge section has air leaking somewhere in cabin.
2. Fan not function
3. Gasket sealing not fully seal