Upright Frigidaire LFFH17F7HWH Freezer issues

We replace the thermistor, the control panel, the defrost thermostat and heater and it’s still not working right. Back coils where thermostat is shows frost on the small tubes. Temp shows 86. It’s getting cold inside but don’t understand the temp and the frosting up behind the panel. Is that normal after having it off over 12 hours to be fixed?