My GE Adora freezer section constantly gets down to -5 to -9 degrees, when the setting is 0.

I would advise replaceing # 4 AND # 5 thermistor . The # 4 , tells the main control board , the temp of the coils , if they need defrosted , when they are thru defrosting . This thermistor is the 1 " long , torpedo looking piece , clipped on the top left of the coils ( remove the inside rear freezer panel ) , with 2 white wires going to it . Part number WR55X10025 for both . The # 5 thermistor , located at the bottom of the freezer , slightly in front of the drain , also with 2 white wires going to it , slid into a housing . This thermistor , is the freezer thermistor , which tells the control board , the freezer temp and when to cycle off due to selected temperature .