Question about Xiaomi Mi Air Purifier Pro

Hello. I purchased two Xiaomi Mi Air Pro devices approximately one year ago. Initially I was really satisfied with the quality of air purifying and low level of noise. Unfortunately, after 1.5 - 2 months of usage, both devices started to produce a substantial noise even if device and its major fan was switched off. The only way to stop the noise was to take off the power supply. I googled the issue and found that this noise is made by air quality sensor fan. Please let me know if it can be fixed or replaced. Thanks!