Intermittent freezing tem in fresh food section

Hello
The first thing I would do is examine the evaporator assembly, make sure you have an even frost pattern across the coil. Sometimes a sealed system issue or starved evaporator ( low refrigerant charge ) will cause freezing in the fresh food section. One you have eliminated a sealed system issue, here are the other possibilities.
1) Is the damper closing ?
2) Verify thermistors are within proper range ( See ratings below in technician sheet )
3) Check door seals for leakage .
Go to page #42 in link below for complete diagnostics.