The avatars file simply had the wrong anim type for a couple of them.
Not entirely sure I got all of them, though.
Thanks, it's now in. I've looked over that bg2 commit and ported the remainder of the fixes.
I noticed we had a line on the bg1 todo listing the missing animations and it is now almost clear. If you find the time, please take a look at it:
* Missing animations - Ankhegs, various Ghasts, nsimlg1e, nsimlg1, nsiwlg1, nsiwlg1e
Ankhegs I've seen in bg2, but I know the original hardcoded some extra animations, since they do all that burrowing (meaning you can ignore them).