how can i fix my samsung sr-s2028cvw?

all works fine until the freezer comes down to temperature.After this the fridge continues to work but the freezer wont cut back in on temperature rise.If switch it off then on again everything works fine until the freezer hits set temperature then the same thing happens . Got it running on a timer to drop the power and start it again(not ideal) this all happens with no fault code displayed. Would be very gratefull for any help.