I recently completely wiped my mibox (original model) and started over as it had been two years and it was starting to slow down, I decided it was time to refresh.
After the reset, I plugged in my thumbdrive that was working flawlessly before, and all seemed fine for about a week. Then the mibox started saying that the drive was ejected. I tried removing and reinserting, tried a different USB Port (I was using a hub) and even tried plugging directly into the unit without the hub, nothing seemed to work. I restored the system again, and then it told me that it would not read the drive again....
So I plugged the drive into my PC and Windows told me that the drive was corrupted - I did a search and found that it was a common problem with the drive that I was using.
Instead of being upset, I took this as an opportunity to upgrade so I purchased a 1TB Toshiba USB Hard Drive (it was actually cheaper than the thumb drive was!) and plugged it into the mibox. I formatted it as internal storage, and started installing my apps and moving along. Everything was going well for about another week and then I got the same error, that the drive was ejected.
I did another search and found that sometimes ES File Explorer and other explorer apps that are out there cause this to happen, so I uninstalled them. Rebooting the mibox does allow it to "see" the HD and work properly, every time....but after a bit (sometimes minutes, sometimes hours) it always throws the same error and I have to reboot again.
Before anyone starts saying "get rid of the mibox," let me stop you right there - the forums where I read about people having these issues were on a Shield TV forum, so the problem is apparently an AndroidTV problem, not a mibox problem.
Does anyone have any ideas of what else I could do? I saw a post stating to try reformatting the drive to Fat32 instead of NTFS, I might try that soon....
Es File Explorer is known to be garbage.
Try Total commander or Root Explorer.