I just turned on my shield yesterday morning, after no update that I know of, no changes since watching it the day before, and it completely had a mind of its own. Flicking between items, going up and down, into the menu and out, and more. See video attached.
I unplugged it completely: power and HDMI. Issue remained...
Not sure of settings and info (can't find the OS because I can't control it...)
It's really quite annoying. Any suggestions appreciated.