My box was locking up increasingly frequently (when not in use, never when playing a film). Locked up maybe every few hours to maybe three or four days at random (required a re-boot every time).
I’ve replaced my nearly full (USB attached) 2TB WD Passport with a 3TB WD Passport - problem solved, it’s now rock solid.
I’m pretty sure the 2TB drive is OK. I’ve previously tried re-formatting it and copying all my files back onto it. It didn’t make any difference to the reliability.
I can’t believe having a nearly full drive causes problems.