MZD2766 GE - A puddle of ice forms at the bottom of the freezer

You need to check the drain line for blockage.

I see you said you looked and the water valve is off but the only that I know of this happening is a defective water control valve. Like a dripping faucet that when off slowly drips until the ice forms and then one the ice maker dumps ice and tries to refill the water goes in every direction. Unplug water valve to confirm what I am saying, Tell me if it continues to leak. Sea Breeze

Have you had any cooling problems coincide with the ice problem? if no evidence of temperature variations, you either have a crack in the ice maker mold, causing water to drip into the ice bucket. Or you may have a bad water valve solenoid, not closing completely when the ice maker stops calling for water, overfilling ice maker into the bucket, and further down your freezer.

those are the most common problems, though other odd situations could also be a problem.

Make sure the condenser fan is working.

Here I am going to give you a lot of information. Because of the leaking your defrost condensate drain is most likely the reason. All on the page below may not be for your situation and some refrigerators do this over a period of time and the the water has no were to go but the freezer during defrost. Click on link below, Thanks, Sea Breeze
HOW TO FIX A LEAKING REFRIGERATOR OR FREEZER

Unclogh the drain hole inside the freezer in the bottom of the bakc wall pouring hot water until the ice melted and keep pouring until goes through.Repet this every 3 or 4 months to keep it clear.

drain in bottom rear of freezer is stopped up deice and use turkey baster to force hot water through drain

More likely, the defrost system has failed.
There are three components: Defrost timer, a defrost heater, and a defrost bi-metal.
The timer can be located either in the food compartment, on the rear of the unit, or behind the kickplate. The heater and bi-metal are located behind the freezer rear wall (or freezer floor, depending on design). It's easiest to unplug the fridge overnight, with the freezer door open, to melt all the ice that has developed. PRIOR to doing all this, please ensure that there IS ice forming on the wall of floor of the freezer! Let me know. I hope this helps!

In back of the refrigerator behind a removable panel you will find a hose going into the drain pan under the refrigerator. Check and make sure there is no obstruction in the hose which would back up water into the freezer. After the drain hose is cleared the freezer should be defrosted and ice cleared from the drain area in the back. You can direct some hot water with some bleach in it through the drain to insure it flows into the pan.

you have a clogged defrost drain, or your ice maker (if so equipped is leaking. clogged drain can be remedied removeig drawer , andmelting ice build up behind rear panel of refrig, you see an aluminum trough that the water drips down,using a hair dryer melt all thatice out of the way to clear the drain tube(i use a steam machine i purchased from infomercial works extremly well