Try pushing down the metal housing against the circuit board and see if the missing row gets any better. Your symptom resembles some of the defective displays that have poor contact between the glass that has liquid crystal on it and the circuit board that has control circuit on. There are 6-8 metal tabs that hold these two pieces together. If these tabs are loose, your display will not show some pixels. If they are held together but the conductive rubber strips between them is out of place, you may also experience this symptom. You are putting a huge delay in your loop already so I don't think it is refreshing-related problem (refreshing too fast).