Posting this here as it seems this issue has not been resolved yet:
What I guess is going on is either:
Ladybird finishes flight preperations, that ladybird then dies in the same tick, flying away was queued already from finishing preperations and is run.
Or:
Ladybird finishes flight preperations, that ladybird then dies in the next tick when it was planning on flying away, flying away was queued and is run.
(It's still only guesses, only the devs can unbox this mystery.)
Edit: Either way the 'flying-away' part does not check for the creature to be alive, I think.