I recently replaced the defrost heater assembly. My drain plug in the freezer keeps clogging up and I have a river of ice in the bottom. I have cleaned out the ice and blew through the drain plug to clear any obstructions and it keeps clogging up.
So if I read you correctly, the floor of the freezer has a layer of ice, which then proceeds to occasionally drip onto the kitchen floor? Did / do you have any ice above the floor, i.e., on any of the shelves or food? If no, proceed. I cant be certain by the schematic for your model, but you should be able to see the the drain hole without having to remove the false wall in the freezer correct? Im not sure what you used to blow through this drain, but try this also. clear out the ice around the drain hole, then pour some hot water to melt any ice in the hole. next, take your fattest finger, stick it in the hole, move it forward and back a couple of times, and the water should go right down.
If that doesnt solve your problem, write back and let me know what else you’ve noticed or attempted. it could be a problem elsewhere.