I believe the drain pump is designed to shut the machine off, if it senses a problem. I believe the problem was too much water going down the drain, more than the pump could handle perhaps. During operation there was more water dripping than seemed normal, though not a gush, just slow drips.
Using a mirror I detected pretty large cracks in the bottom of the water pan. I ordered and replaced the water pan. In order to replace the water pan, the water pan pump must be removed from the bottom of the water pan. The two hoses and drain cap need to be switched from the old pan to the new. It was all easy peasy until it came time to reinstall the pump to the bottom of the pan. The o-ring on the pump apparently had stretched out, preventing it from fitting back onto the water pan. Believe me I tried to force it. I visited three hardware stores before finding an o-ring with the same thickness (3/32" ) that fit the bill. Using the correct o-ring, the pump went on smoothly and my machine is making ice better than before. Though it's only been running for two days, as I type this.
So I hope the cracked water pan was the culprit.