I tried searching on various forums and couldnt found any similar case reported. I received Android 9 update Mi Box 3 last week. Since then i am facing a major issue of remote getting disconnected after a few hours of mi box's sleep.
I replaced the batteries on remote just to be safe but still, after 3-4 hours of sleep the device dont respond on remote's power button or any other button for that matter press.
Second surprising issue is the TV dont register MIBOX as a HDMI CEC valid device while the Mi Box is asleep.
The above mentioned issues started after I updated Mi Box 3 to android 9 last week