This may be anathema to some, but I upload to all my networks, including WU via a Meteobridge. I actually do that for redundancy, because it's easier to keep it running than the iMac, just in case. I feel like the data isn't corrupted because it's good everywhere else: my website, other wx networks, even on most places at WU, just not on the main place it's displayed: on the dashboard. I've sent some more screen captures to "Kari" at Wunderground, and I'll see what happens next.
This is one of the crazier errors I've seen go unfixed on their site for a long time . . .