GE refrigerator not cooling in upper half

Our GE frig Model: DFE29JGDCBB
Ser. No: LA516606, Sept 2013, has stopped cooling in the upper half. The veggie and meat drawers are cool to the set temp of 34-deg. The upper half is about 68-deg.
I remember within a year after we purchased it we had it serviced under warranty and they replaced some sort of circulating fan that had a factory defect in it. It was located behing the drawers and covered with a plastic shroud. I took off all the drawers and there was some ice buildup behing the meat drawer near what appeared to be the cooling vents.

Any help? If you think it's the fan, how can I debug this and where can I find a replacement part?

Thank you,

Bill

 

That's a pretty involved dual evaporator two fan refrigerator.
You should be able to feel airflow. I've left a link below to the service manual.
Much easier to see rather than me describing it.
Usually the door switch needs to be held in to test fan.

Sears Parts Direct - exploded views
Downloadable service manual