Well known issue; the small fan on the SBC is pretty shitty. Contact customer support and they'll send you out another
It's been over a month and they still can't figure out the issue. It's very frustrating, they sent me a new fan and it keeps running at over 5,000 RPMs. They sent me a new firmware and that hasn't resolved the issue. I have 4 of these running and the latest run is having all the issues.