SAMSUNG HEY HEY
Something I know about..

So what you are saying is that the Fridge works for a while & then stops cooling with no error message yes?
Well if you turn the power off & on it should start back up you should be able to hear it click & the compressor restarts

Powering the unit off & then On Resets the PCB
& it should work for about 4 hours
4 hours is the default for its first Defrost..
If its turning off (not cooling) after 4 hours
theres a defrost problem

Being a double evap unit It starts the defrost in the fridge section first & when & if its done (with out any problems) it then moves on to the freezer
So i would check the fuse link on the evap first
& then the heater itself & then the drain heater
if you find nothing in the fridge compartment wrong then you move on to the freezer compartment
..Any questions just ask
Ps still have got some service manuels if you have the model number..