Whether or not this is actually a bug, I should have mentioned it a while back...
But anyway, in the more recent betas, Vires will sometimes appear on un-walkable combos for some reason, and that's where they get stuck!
EDIT: I think this one is fixed for sure now.
Vires appearing on unwalkable combos?
I've yet to notice this.
OK, fixed.
so do Keese