Hi everyone I have discovered a trick to resolve the disconnection issue of the USB stick on MiBox S android 9.
- Remove the USB stick from the MiBox
- Restart the device (press+hold power button)
- Reconnect now the USB stick into the MiBox s.
- Restart again.
Done!
It probably will happen again; I'm pretty sure that was simply the USB stick overheating and shutting itself down to prevent damage.