Several Mi A1 owners report this on online forums, including Reddit. The news is remarkable because the Xiaomi Mi A1 has run a beta period of about two weeks.
In such a beta, interested parties get a first version of the new software, with the aim of testing it for bugs. Various different bugs were reported by users, but one of the most notable ones is the battery drain, and judging by the reports that have been coming in, the battery drain bug is closely connected to the phone’s Bluetooth function.
We currently do not know when will Xiaomi continue releasing Android 8.0 Oreo for the Xiaomi Mi A1, but those bugs will, hopefully, be amended soon.