Red graph & 'Sleep as Android wants to turn on Bluetooth' popup every few days with Mi Band3/MiBandTools


I have this issue that every few days I get a partly/completely red sleep graph, and when I unlock the phone I see a popup with ‘Sleep as Android wants to turn on Bluetooth’.

I am using a OnePlus 6 + Mi Band 3 + Mi Band Tools. All the battery optimizations should be turned off, app is running fine. It just seems that for some reason Bluetooth turns off/looses connection at night.

What could be causing this? Judging by the popup, could I somehow give Sleep as Android permission to turn on Bluetooth without me having to click allow? Or is there some other fix for this?

Thank you!