So I upgraded both my AirGradient ONE’s to the new v9 boards a few months ago. I pulled all parts from old boards to the new and everything worked great. Today I updated both the boards to the latest firmware 3.0.0 and now one of units shows -428.8 as temp and -% for humidity. Im 100% sure the SHT is fine because it worked great before the new firmware. I also tried another re-flash with a data wipe and that did nothing. The only thing I can think it may be is the temp sensor is a SHT3X (31 I think) not a SHT40.
Any help is appreciated!