I have had a similar call like what you are having. the customer had stacked Manatowocs' and were water cooled. The plumber plumbed all the drains together, including the condenser drain. One day I recieved a call of low production. To make the long story short, the drian became blocked and the warm condinsate water was backing up into the bin as the head purged its sump, and between harvests the bin then would drain out.
Just a thought that you could have a problem ouitside of the ice machine.
I had same problem once and what would happened was that at night when everything shut off in the restaurant. The machine cold water supply was hooked up about 20 feet away from hot water mix valve which was leaking by and slowly the heat would migrate into the cold water side causing it to warm up the supply water to ice machine. It took alot of scratching my head tofind it hope it also your problem.
If everything is the way it should be, and water is good. The power is not being shut down in error. I would say you are a victim of evaporator separation. This would not be completely uncommon for a hoshi.
Once I had a case where a new employee was turning off the wrong breakers at closing time
Most icemakers here are having an *easy* summer. Water temps here are normally 85, but are 75 this year due to unseasonal weather.
Do these systems use floats? If so, turn them off and see if the floats continue to let water in. If so, and the water level doesn't get any higher in the reservoir, check for water leaks. This could kill the capacity if they're losing cold water out of the evaporators and the floats are replacing the water with 73 degree water.
You can also check this by turing the machine off, then turning the water off to it. If the reservoir level drops, you've got a leak.