How are you using the MiBox (as a streamer only)? What apps do you have installed and/or use? Have you tried force quitting apps to see if it has any effect?

I have a MiBox with stock firmware and only have a few streaming apps installed (PS Vue, Plex, Netflix, etc.) and I've not experienced the issue you're having.

In my experience with the Mi after running basically every factory & beta OS, using wired Ethernet, running at both 1080p/4K, etc. Nothing, and I mean nothing, can really "fix" it. Other than of course Xiaomi coming to the rescue & releasing an actual stable update (LOL!).

At 1080p its manageable (w typical headaches), at 4k its barely functional. It spits & stutters along, YouTube sucks on it & bogs down, casting is hit or miss, etc. Which is funny because my budget Samsung 4k TV can do all of those things & not even hiccup.

Its a god damn shame really as I think the hardware is capable but the software & efficiency just plain sucks ass. And the only other alternative is a box that's twice as expensive. I'll prob end up getting a Chromecast Ultra & using the Samsung's OS for IPTV, Netflix, etc so I can actually take advantage of my display's capabilities, instead of limping along with this thing. I tried.

I haven't rebooted my Mi Box running the latest beta in weeks, it works very well right now. Maybe try wiping cache or do a Factory Reset and clean setup, it should work much better than what you're dealing with.

My post/advice is probably worthless because I don't own a MiBox but have you tried a factory reset? Are you using the beta builds people have been talking about?

Edit: Sorry about that! Disregard it. 😂