Oh! Do you have any screenshots for this? Or a recording? I need to personally confirm this before adding anything, but I have Astarion in all my playthroughs at the moment.
Funny. Same but mirrored everytime killed him except one time when he admitted his vampiric nature in dialogue with Dark Urge very soon after one incident with bard.
Here's the video. I don't have save where I kill Astarion but I think I've captured the problem.
