APM6530 FF Fault?

My integrated appliance works ok after defrosting the whole unit but after a couple of days the fridge temp goes to H and stops working. The freezer works ok and maintains the correct temp but the fridge stops cooling.
I then check inside the freezer behind the fan panel and the grill part again seems to be frosted up once this has been defrosted all works fine but I am having to do this every week to keep the unit working can anyone please help solve this problem Thanx