Hello,
I am Francis, and welcome to Just Answer. I have been a field service technician for the past 31 years servicing all kinds of branded appliances. I am sorry to hear that you are having an issue with your unit.
This is sounding like a lack of refrigerant.
The unit is not frostless. The whole evaporator coil starts at the freezer area, then would travel up to the fridge area to cool the back wall inside the fridge.
If the freezer is cooling well and the fridge, which is the last part of the evaporator coil is not cooling, it means that the evaporator coil is not cooling up to the very end of its pipings, then it lacks refrigerant. The refrigerant inside is no longer enough to cool up to the very last pipe of the evaporator coil.
I am sorry but this is not a do it yourself process. You would need a tech to add refrigerant on the unit although you have to ask him to find first the leak because refrigerant would not escape in a unit unless there is a leak in the system before he charges it again with refrigerant.
I would assume it would be a very small leak because the freezer is still cooling.
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Please stay safe.