Without thinking much about the implications, I updated to the Sierra GM the other day. I had a rough first hour with it, a bit of cleaning up and updating calmed things down. But WeatherCat was not happily talking to my weather station, WC actually quit a couple of times saying that it could not talk to the weather station. My graphs were showing about 20% dropouts. No update to my driver. Hmmm....
Decided to unplug the USB and let things settle down for a day, then plugged the USB back in, re-selected the device path within WC, and it has been happy ever since. I can't really account for why this would be so, but I'm happy with the result.