Whirlpool wrx735dhz03 Ice maker help

I have a Whirlpool refrigerator model wrx735dhz03 with a built in on the refrigerator door ice maker. I’ve had the refrigerator for just over two years and have now replaced the ice maker unit 3 times. The problem is always the same. It makes ice normally for about six months but then begins to form giant masses of ice in the bottom of the ice tray. These giant ice bergs are best described as cubes frozen into pools of water at the bottom of the ice tray. I was guessing the ice cube tray was being overfilled, or the ice storage drawer was not consistently cold and was allowing already formed ice to melt and refreeze. But, with each new ice maker I install the cycle starts over again… good for six months then ice bergs. And so on. I am using Whirlpool OEM W10882923 ice maker replacements.

I have also done the following: replaced the shutoff valve, measured the water pressure entering the refrigerator (which is at a consistent 35 to 40 psi). Interior of the refrigerator measures 38F on the top shelf and 32 on the bottom shelf.

What else should I be looking at? A thermostat somewhere? Electrical problem?

Any help is appreciated.