Do I Have A Sealed System Issue?

My 10 yo French door refrigerator won’t get colder than ~42 degrees in either the fridge or freezer. All of the onboard electronic diagnostic checks come out good, the coils under the unit are clean, both fans are running, and the condenser is running an warm (not hot). But, the evap coils are frozen on the top right 1/4 and clean and dry else-wear, and there appears to be dried green sludge inside the backside of the unit. (See pics). What are the odds this is a sealed system issue and I need a new unit?