Playing through the game right now, and I'm really enjoying it. Just finished the Sebastian chapter, and I noticed a couple of weird things with that. First, there's a forest tile on the northernmost row of the map toward the left side next to a cliff. On the cliff there seems to be a Ballista, but not only is it inaccessible (due to being on a cliff), sometimes the sprite seems to glitch and it just shows up as a mess of color. You can actually see it in Mangs' playthrough in the very top left here, though I don't think he noticed.
Speaking of his playthrough, I'm also curious about something else. Did leaving Marcius alive change any of the other enemies on the map? I am playing the same patch (1.6.1), but instead of a hero and a warrior near the boss, I got a great knight and a sniper.
Anyway, keep up the great work!