Found root cause of water distributor leak: White plastic shaft that goes through the red double lip seal in center of water distributor housing was worn. A groove was worn into shaft ~ 90 DEG around. This short shaft connects motor to distributor wheel. When cycle called for water distributor motor to do its thing, water would leak into bottom of machine, raise the float and trigger E15. Was thrilled that Appliance Parts Pros had the exact assembly I needed. An invaluable aid was the YouTube video with great camera work showing exactly how to tackle repair. (ref: "How To: Bosch/Thermador/Gaggenau Sump Assembly 00668102")