...BUT this affects only ones I've killed previously and not ones that I've never hit before...
Visual glitch.
The game cell in which the
hawk was killed has not reset. You should also notice that the corpse no longer rests where it initially fell.
Technically, the
hawk has not yet re-spawned.
Technically, it isn't actually there. It will, however, whisk your arrows off to neverneverland.
Best to just leave that game cell for the required time and let it reset.
On a side-yet-related note: Why, oh why, did Beth make the reset timer 720hrs? Anyone? Anyone?
As TES4 was 72hrs, this new 720 seems like an unintentional keystroke. I can't fathom it being a gameplay decision.
30 in-game days has the roads stinking with corpses. Keep passing through and the cell will never reset.
Bueller? Bueller?
Edit: This is not an issue introduced by 1.3, as it was seen in v1.1 as well.
It's simply a visual glitch that has yet to be fixed.