Intermittently (maybe once every 5 or 6 washes on average) the water never circulates. Initially, the water drains, the tub fills with water and then there's total silence as the timer counts down as though everything is working OK. The soap dispenser opens at the appropriate time and the dishwasher drains and refills at the appropriate times, and the cycle completes, but there is no sign that the water has ever circulated. The Bosch technician has already replaced the controller board, but this did not solve the problem.
Any ideas?