Liberate Spireton Bug-Uncompleteable

[dudedaniel]

I've been experiencing a bug with the Liberate Spireton optional quest that renders it impossible to complete.

No matter how I approach it, whether I sneak in to disable the mechs beforehand or not, or agree to a frontal assault or not, it simply does not complete.

I can tell the Order guy that it's time to assault, even after killing everyone there, after which point he cannot be spoken with.

I seem to gain a chunk of experience after it anyway; In my save I reach level up just after finishing killing everyone there, including the disabled mechs or not, and after a several second delay after killing the last enemy, so it's likely mission xp and not "coincidentally the combined enemy xp is enough to level up"

Shortly after combat finishes there remains 1 red "enemy alerted" sign on the UI that gradually disappears, and seems to be located around the center near the giant golden globe, suggesting there is an enemy that spawns underneath the map that I can't reach. Firing wildly doesn't seem to alert them.

I've tried fixing this every way I could think; Leaving/Reentering the area, saveloading, fast travel, briefly attacking the Order units, including the named one...but nothing seems to work.