I've looked a bit at the data from the 8m sonic. I plotted u,v,w components from 7m&8m as a function of wind direction. If the etherant were causing flow distortion, I would expect a signature that depends on wind direction. I also would expect vertical velocity to have a negative bias for winds into the array. What I see is u.8m being lower than u.7m, v.8m being equal to v.7m, and w.8m being higher than w.7m, all independent of wind direction. Thus, I do not believe that the etherant is the source of the low winds at 8m that we've been seeing.
The next step is to replace this sonic.