Freezer to cold refrigerator not cold enough

Refrigerator: Freezer not cold enough. Defrost system problems, dirty condenser coils, fan failures, leaky door gaskets or control problems can lead to your freezer not getting cold enough. ... The frost buildup blocks cooling air paths through the evaporator so the freezer doesn't cool well.
https://www.searspartsdirect.com/diy/symptom/refrigerator-repair/1234589/freezer-not-cold-enough/ref0002

Fans inside freezer and at compressor working? Any frost buildup on inside back freezer wall?

If the refrigerator is not defrosting the defrost heater assembly might be burned out. Several times a day the defrost heater assembly turns on for a few minutes to melt away any frost that may have accumulated on the freezer or refrigerator evaporator coils. If it fails, frost will build up on the coils and eventually no air will be able to travel through the coils to provide cooling. The defrost heater can be checked for continuity. If it doesn't have continuity it should be replaced.
Next chance is the defrost thermostat might be defective. This signals that the coils are cold enough. If the coils are cold enough the defrost heater will turn on. If the thermostat is defective it may not be able to sense the temperature of the coils and then won't turn on the defrost heater and create the same problem you mentioned. It can be tested for continuity when it reaches the low temperature of its operating range.
You may also have a bad main control board that tells everything to work when it is supposed to such as telling the defrost heaters to activate or interpret the thermostat message that it is time to defrost.

Good luck!

Do you see any ice buildup on the back wall of the freezer or behind it?

Most problems with side by sides frosting up is due to failure of the defrost heater in the bottom of the freezer section behind the panel inside.

Possibly a defrost problem or a fan that's not running. Any frost buildup on inside back wall of freezer?

You will have to check the defrost timer to make sure it is turning if it is working properly and you are getting power to the defrost heating element below the freezer coil it should get hot if you have a 115volts or so to the element and it does not get hot then you have a bad element

too much ice bulid up will stop enough cold air being blown into the fridge.Try turning it off letting all ice melt then turn it back on again and set thermostat at a lower temp.There may be ice you can't see.

How old is "OLDER" ? If there is no frost buildup on the back wall of the freezer you could have one of two problems. On older units the compressor wears out with years of service and no longer pumps efficiently. Or it could possibly be low on refrigerant charge. ether one of these two problems is a sign that is time to update to new unit.

If you have frost buildup on the back wall of the freezer section you then would have a problem in the defrost circuit attributed to the timer, defrost heaters or defrost thermostat.

Is the fan in the freezer running?? Is there frost on back panel of freezer??