Is it an RS21 or similar?
Samsung had a safety bulletin out over that particular range pertaining to the defrost circuits in the fridge compartments.
May be worth ringing their customer service department with the model and serial number.
I would suggest a manual de-frost over a period of 72...
Need to know the state of the ice on the evap, whether its even?
Is the compressor running hot?
The condenser at the back, have you got a temperature drop off between compressor and filter?
I've fixed plenty of fridges with little more than a phone call or advice.
I recently fixed my samsung HD telly with 4 capacitors that cost a grand total of £2.90 from Maplins
Yeah....I should've binned them :lolol: