I have the same issue with the same model fridge. Did you find a fix?

There is a jiggery pokery fix, note that I have never tried this but have see others say that it works.

First make sure your drain line is clear/clean and there is no dust etc. slowing down the flow at the drip tray end.

Often it is a good idea to flush it out with a 10% bleach solution.
Flush it, let it sit for 15 minutes and do it again. Do this a number if times.
Often crud grows on the tubing walls and you are trying to kill it and flush it out.
Just be careful that you do not overflow the drip tray.
Also wear old clothes unless you are into the tie dye look.

Jiggery Pokery Method
If the unit has a calrod (black/greyish defrost element)
Get a piece of bare 14 or 12 gauge wire and wrap it once or twice around the defrost heater.
Then position the other end so it goes down the drain tube about an inch.

The idea is that during defrost the wire will also warm up some and melt any ice that has formed.

I have used the advice provided by Denman and am happy to report that there has been no icing since May. I am most grateful for the advice.
Aglaser

Thank you so much from saving this Mom from unnecessary repair bills! Without these gentleman sharing their wisdom, I would be sunk!