Xiaomi has released a new firmware update for the Mi Band 5 activity tracker. The software has been pushed out to deal with problems with the accuracy of the sleep-tracking function, with a few other minor additions such as extra language support included. It's likely the update will eventually make it to the international Mi Smart Band 5 variant.
https://www.notebookcheck.net/Xiaomi-Mi-Band-5-receives-new-firmware-update-to-fix-sleep-tracking-issues.509517.0.html