I have seen this with Provoke and random other abilities that will sort of partially fire, where their animations will play and it seems like they went off yet their effects aren't applied and the cooldowns isn't activated forcing me to use the ability again once I realize that it never went off.

My guess is it is a goof with client to server communication where the client thinks you used the ability so it does all the "you activated X ability" stuff but the server never receives that info so the effects are never applied or it resets at the next server tick.