This will be a blocked drain hole in the freezer thats causing this fault.
Now the back panel inside the freezer is split into 2 halfs. You need to remove the bottom half so this will come off without messing with the panel behind the ice maker.
Empty the freezer and remove the plastic cover at the back at the bottom (if fitted)
Then remove the screws on the back panel either side.
Then theres a screw in the center of the panel top and bottom.
Remove them as well then you should be able to remove the panel and clear the ice from the drain gutter from there and make sure the drain hole is all clear.
But if you cannot remove the panel then another way to clear this is a total defrost. Turn the appliance off for 24 hours and leave the freezer door open. This will allow the ice to melt in there. But this way you need to either run the food down or find somewere else to keep it.
Try that and see what you find and let me know.
Ok were the vent is at the bottom at the back thats were the drain hole is.
If you cannot remove the back cover then what you can do is widen the vent slots and use a scrwdriver and chip the ice out from there. Then try and pore boiling water through the vent and keep doing this untill the drain hole is clear.
As once you start melting the ice you will soon see the drain hole.
So thats another way of doing this without removing the complete back panel.
Ok the service info shows it as 2 halfs but as you say its 1 piece then it shows the sevice info is wrong.
Can you post a picture of the inside of the freezer so i can see the full back panel as the food in the picture covers most of the panel.
I see the question is still open, Is there anything else you need to know? If so then just get back to me.
If not then could you please remember to rate the answer and that will close the question.