Frozen evaporator coil

Side by side model. Original issue was neither fridge nor freezer would stay at the proper temp. Freezer was melting ice and fridge was over 50 degrees. Cleaned coils under fridge. Took apart the freezer walls and found the coils in the freezer were totally frozen. Defrosted with hair dryer and replaced the defrost thermostat. Both set to factory settings. After 5 hours, freezer is at 32 f, fridge is at 40 f, but find the coils are already freezing over (pic attached). Is this normal since the defrost cycle is supposed to be around 8 hours?