Here are some parts breakdowns.
I could not find an exact match to your model number.

Since the freezer is getting to warm I would say that the thermostat is the most likely culprit.(Item 3 Section 2).
Sometimes they can get sluggish.

I am assuming that everything else runs and sounds OK.

You may want to check the time it takes for a defrost cycle.
Should be 20 to 30 minutes. It usually says on the timer.