How difficult do you think it might be to take a network of 2-3000 stations and scale it to over 10,000 and beyond in a very short period of time? If only the WF upload to WU is the issue (ie. third party uploaders still work fine), then it is very likely a WF server issue. As they stated over on Missing Data - #10 by dsj,
So if it is on WeatherFlow’s side, it will be fixed.