Got a new TV for black friday, upgraded from an 8 year old 42" 1080p TV to a new 55" 4K model.
Since then the wake up lag (mibox being literally unusable until reboot) is gone.
Just this morning the mibox had been idle for 12 hours. Turned it on, no lag. Works great, without needing to reboot.
I have had the same thing happen as OP. I got a new 4k tv and plugged in new 4k compliant cables and my mi box issues are gone. I had wake up issues before and I also had sounds issues with dolby digital dts (5.1) skipping. The skipping is gone. I am completely amazed. It is like a new box.
My TV has cec and I have the wake up freeze issue, but I use cec for other things and it works fine (like Chromecast)...
Edit: well I had cec turned off on the mi box. I guess I'll turn it on and see if it makes any difference...
Mine worked flawless before Oreo.. it's simply a shitty update
My TV is old and doesn't have CEC but I still have the issue on occasion
cec works fine for me with sony 900F. Mibox would not wake from sleep on occasion, rarely..like once every 25 or more starts, but haven't had the issue since update a couple weeks back..probably 20ish power downs
Maybe the issue is with HDMI CEC and older TV?
I have a 10 years old TV and CEC off, works perfectly too...