I am having the very same, very frustrating, issue with my DW80H9930US. I have replaced the entire motor assembly, main board, and water pump with embedded heater (I was also getting an HE1 error). I read one person's solution was to add a very thin rare earth magnet to the underside of the water vane magnet to increase magnetic strength for the sensor (he claims it weakens over time). I haven't been able to get a proper magnet where I live, but I did try a less than ideal magnet (a bit too large and not a rare earth magnet). Apparently, most hardware stores carry them though.
A bad inverter board was also suggested in another post; I have not tried to replace that part. The only other part in question may be whether or not the plastic track on the water vane is stripped somewhere. Mine seems to be skipping as it reaches the back of the dishwasher ( I was able to watch it while I held a knife in the door latch to keep it operating).
The magnet solution may be worth a shot...at least it's cheap.
Please post if you get a solution
I feel your pain!