So are the lights flashing all the time or is it just now and then they flash?
Does the temperture seem to be holding as it should be?
Also as to the ice on the evaporator this is normal as they start to frost over as soon as the compressor kicks in as its the gas being pumped round so frosting starting to form around the evaporaor this quick is normal as if it wasnt then there wont be any cooling in there.
Ok if the lights are flashing like that then its either the defrost heater, wiring connections for the heater or the control board at fault here.
To test the defrost heater you need to access the inside of the freezer again and there you will see the defrost heater wrapped around the evaporator. Follow the wires to the top and then you need a multi meter to test the heater. Its around 500 ohms roughly. If faulty then you need to replace the heater.
But if the heater and the wiring connections are fine then the control board at the top will be the fault. Now for this the board will need to be replaced but these are now a conversion boards so you need to alter the wiring as well. It will come with full instructions and wiring. So just be aware the boards are not a direct replacement but a conversion now.
So check the heater and wiring first and see what you find. If you need anymore info just get back to me.