Water line freezes and have to use blower dryer to unblock line

[wildimaginations]

Here's a challenging question.

This customer has GE refrigerator that has an erratic freezing problem on her water line in the refrigerator.  It's worse in the summer time than in the winter.  She puts the blower dryer in the area of the water tank to unfreeze the lines and in about a minute or two, the water flow returns.  Attached are some pictures.

Question:  What is the purpose of the mechanical device behind the bottom drawer??  It seems to be some kind of special cooling fan for meats and such but can't figure it how to control it.  

Is there a factory recommended fix for the freezing water line problem?

Model PSS25SGMABS

[JWWebster]

PAGE 11
Shows how that airflow gets circulated in that ice box

[wildimaginations]

So 2 things can go bad.  The damper assembly or the control board that controls the damper.  It seems that the board is the most likely problem wouldn't you say?

[JWWebster]

The control board only opens and closes the damper using info from the thermistor. A small amount of current is continuously fed to the thermistor. As the temp changes the voltage is affected because the thermistor's resistance is changed. That is how that fancy control board knows when to send cold air. If that thermistor is off a little that could affect the performance. Here is Shawn's excellent video. How to check thermistor:

[niobrara]

Board and thermistor