Didn't help overnight drain here, at all. Have no drain during the day. Use DND overnight, will try flight mode, unless I flash MiuiPro already today. :)
Still draining battery overnight on Mi6. Not during day. May be DND-mode that I use. Will use flight mode tonight and see if it will stop. If not I'll probably flash MIUIPro.
It is however a well known issue with Oreo 8.0, not 8.1.
No lag here but have the same drain during night. It's RCS Phone doing it for me. Same for you?
Gonna try and clear cache etc.. and see if it fixes itself.