Normally, you abort missions on craft or entrance tiles. Did you use exit tiles by mistake?
There is no craft in this mission and no other entrance area. For story and design reasons, X-Com units are spawned in random places using X-Com nodes (but there are no associated tiles, since these places would not be valid exit points). So this is set up exactly as intended and works as designed, except for the incorrect "0 units in exist area" message.
The game doesn't recognize this mission as exit-relevant and hides the "units in exit" label.
These definitely
are exist tiles (they have type 13 in byte 59). I understand that it was not predicted, but they should be recognised as such.
Exit tiles can be used for missions with a next stage (e.g. tftd alien colony) or for missions with escapeType = EXIT (1) or EITHER (3).
Well, I can't do that here.
Bottom line: the mission works fine, it's several years old. I am not willing to alter it by adding a second stage or something, because it doesn't make sense. Using standard entrance area like in alien bases is not an option either. And I can't use "escapeType: 1", because running away does not equal victory here.
Sorry, I'm not trying to be difficult, I just can't see what else I can do - but I am open to suggestions.