I'm not sure if it's Evac all bug, LW2 bug, general XC2 bug or a cocktail mix of mods type of bug... but it does regarding evacting so...
I'm on a mission where I need to evac all civilians from an haven and there's 7 turns until firebrand can pick them up. There are 8 civilians, 1 is of course faceless whom I've dispatched of early.
The time has come and I evac them all together with Evac All. They all gone but the UI indicates that there's still one alive.
I loaded the game and did it again this time evacing them one by one. I couldn't see what happened but either one of them didn't register again while going up or just disappeared.

Any idea how to counter this?

Like I've written, not sure at all this is a Evac All bug since it could happen even when evacing one by one (but not waiting for the animations to end (which I think IS a EA feature if I remember right)).

Update: After evacing all soldiers I still got flawless indicator so I guess this is purely UI bug.