when you turn it off your resetting the memory on the control board .
The evaporator plate does not tell the unit to turn the water on that is done via the control board once it goes into a harvest mode.
In the harvest mode the unit heats the evaporator plate to drop the slab down onto the grid to cut the cubes and at that same time the control tells the water valve to go on and to let water into the water reservoir.
If the thermistor never tells the control to go into harvest it just keeps circulating the water over the Evaporator plate, and it makes a bigger slab until it runs out of water till the pump start slurping the water.
You turn it off the slab drops down on the grid ,and when you turn the unit back on it reset the control , and fills the reservoir until the control senses the bad thermistor and it starts all over again .
Ok You need to realize that is why I asked you to watch it so we knew exactly what it is doing .
You are my eyes and ears. if it is dumping water you could have a slab hung up ,partially on the grid ans partially on the Evaporator plate and water travelling over the slab and dumping the water. .
So watch it and let me know what you see.