From Update:

Known Issues

It is not possible to properly progress in the San d'Oria mission The Heir to the Light.
From Emergency Maintenance today:

The following issues has been addressed:

-There is an issue wherein the ally NPC may not warp out of the battlefield once KO’ed and the battle would continue for the 3 nations missions, “The Heir of the Light”, “Where Two Paths Converge”, and “Moon Reading”.
Does this mean that the issue from update notes is now fixed or is it still not possible to progress in the sandorian mission heir to light? I was working on rank 10 in all cities when this nugget popped up and was just about to start this mission. I only ask because the first issue says sandoria only and the emergency maint says all three.