Why does my Bosch SHE3AR52UC/08 Dishwasher run forever?

We have a Bosch SHE3AR52UC/08 Dishwasher. When started, it will run forever. If we start a cycle before we go to bed, it will still be running in the morning.

I've heard of Bosch dishwashers having this problem when the heating element isn't working. That isn't the case here. The water gets as hot as any dishwasher I've used.

One notable behavior is that, eventually, it starts to periodically pause for a minute or so. The sound of washing stops, and the "Active" light blinks slowly and steadily. Then the sound of washing resumes.

Has anyone seen this? Could it be a problem with the soil sensor?