I think most ice-makers have a tray that the frozen ice "cubes" get dropped into. And there is usually a metal lever of some sort that is used to detect "tray full" and turn off the ice-maker.

Simply raising that lever by hand, until it clicks and stays in the "up" position, will normally disable the ice-maker completely. This is in the owners manual, if the refrigerator has it.

As for the frozen mass of ice at the bottom of the freezer, it must be from condensing/freezing moisture from humid air. This used to be "normal" when you and I were children, but modern "frost-free" freezers have dehumidifiers and/or heaters to prevent it.

So cause #1: perhaps there is a source of humid air entering the machine? Possibly from the still-operating (?) ice-maker mechanism? Or from a leaky door seal (or something stuck to the door seal)?

Or cause #2: something has gone wrong with the defrost circuitry. Most likely a sensor has failed.

Cheers