Boy, that sounds like a bug to me. We aren't reading the data properly occasionally. This happens with Threads. I have opened a bug. We are just starting on the next GroveWeatherPi update (adding Alexa, fixing bugs) and will have something in the next couple of weeks.
Sorry for the dumb question. Are the BugWeek February 2018 updates going to be implemented in February 2018 or the week of July 17, 2018? I’m currently running the system using the WeatherPlus board but plan to do a build with the Raspberry Pi, Grove, etc so I can use the Thunderboard I have as well as other sensors that are compatible.