Has done this at least 5 times now.
hold down xbox controller button to shut down xbox 1 x
controller goes off , xbox goes off (I go to bed)
power does not get cut to xbox, it stays in "standby" mode
come back, turn controller on.
click ESO icon to load ESO
ESO shows loading screen of last location I was in, screen goes black. ESO hangs
only way out of this isto go back into xbox menu, load another game on hdd (in my case, minecraft)
exit that, reload ESO - ESO loads fine
will only do this if power not cut to xbox (ie goes in power save mode)