Does the freezer still work OK? Does it stay cold when the fridge gets warm.
Then it could be a few things.
The cooling fan, defrost heater and/or thermostat, Defrost timer.

Just from what you posted. It sounds like the Freezer is icing up and you need
to defrost it manually
If so then it would be the defrost heater and/or thermostat or defrost timer.
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