Ok i finally upgraded to the nvidia shield tv from the MiBox. Both running the latest Orea 8.0 update. However I'm noticing on the shield, it doesn't keep apps running in the background for very long. I was very surprised. The mibox keeps all my apps running for quick access but on the shield apps like youtube, netflix, Directv Now will relauch after going back to it. What gives?
I use to set up the Mi Box to only have 1 or 2 background processes on MM, but now with Oreo it works great with background apps open.
So try the reverse of what I did. Go into development mode (Go to settings, about, and clicking "build" a few times until it says you are a developer).
From there go back to settings and find Developers options. Scroll down towards the bottom to "Background process limit". See if that helps you out.