The Ethereal alien species has a rather annoying habit of blocking and reflecting shots fired by my soldiers. I expected to gleam some insight as to how this ability works after performing an autopsy on one, but was rather surprised not to see anything related to this ability when examining an Ethereal in the unit analysis view (it had quite a few abilities though, so it's possible, though improbable, that I missed the description despite looking for it).
So how does this ability work? Is it related to the range at which the shot is taken (I've never seen them block a sniper's shot)? Is there simply some random percentage for a shot to be blocked? Is flanking a factor?