Bug during Lann's quest line? (spoilers)

Upon defeating savamelekh at the valley of temples, immediately after the cutscene that follows I'm getting a game over due to party being defeated. I can't seem to get past this scene, it doesn't seem to matter what choices I make during this section, the cut scene causes an immediate party defeat after.

Incase it matters I have not reconciled with the mother, I'm full lich mythic and have not romanced lann at all. I've been generally supportive of him the whole run. I don't have toybox or other mods running either.