Please describe the temp range behaviour?
a). Does it get to 31.9°F and then stay around this temp for a long while e.g. ~8 hours and then go up to 57.8°F and stay there for say an hour and then come back down to 31.9°F?
b). Does it just move between the two temps constantly e.g. starts at 31.9°F and then drifts up to 57.8°F and goes back down to 31.9°F etc?
c). What temp does the refrigerator's display panel show when the log shows the high and low temps or are you looking at it after the event?
If a). then perhaps it is a refrigerator compartment evaporator thermistor (aka defrost thermistor) problem.
If b). then perhaps it may be a refrigerator temp thermistor problem (there are two temp thermistors in the refrigerator section).
I realize that the Tech ran the tests and it showed nothing amiss but reading the service data sheet (see below) it says the FF thermistor tests and the FF evap thermistor test only whether they are "out of range" and not that it is indicating the correct temp at the time. To me this just proves that they're within their high and low temperature/resistance parameters and not that they're reading correctly. Maybe double check that the refrigerator temp thermistors are OK. There are two refrigerator temp thermistors, diagnostic tests 00 24 (FF1) and 00 25 (FF2) thermistor test. Evaporator thermsitor test 00 26 (FF Evaporator)
Initially maybe just some general checks if only to eliminate them.
- Check that the refrigerator door seals are all OK and that they're providing a good seal. Place a sheet of paper between the door and the door jamb and with the door closed normally, try to pull it out. It will come out with a bit of an effort but not that easily. It definitely shouldn't fall out by itself. Do this at various places around the door, top, bottom and both sides. Also check the door alignment to make sure that it is straight and parallel to the cabinet in case it's a hinge problem.
- Check that the refrigerator lights turn off. With the door open manually operate the door switch and check if the lights turn off.
- Check that the condenser unit (under the compartments near the compressor) is clean and free of dust etc. If it is covered in dust, vacuum it clean. Dust buildup on the condenser unit prevents the heat absorbed by the refrigerant as it passes through the evaporator units (your model has two - one in each compartment) from being released more quickly as the refrigerant passes through the condenser and this can impact on the cooling efficiency of the system.
Here's the service data sheet anyway, that may also help. It shows how to perform the diagnostic tests and has the wiring diagrams as well.