It's not a new bug in 2.1, it's been a problem since the game's launch if you chain your abilities together too quickly. This is most noticeable with Aetherflow and Invigorate, I've found. Blunt Arrow has it happen occasionally but it's more often that you'll get the other thing where you see the animation, but then it stops you halfway through the animation and you have to shoot it again, which doesn't matter because by then whatever you were trying to silence has gone off.

A similar glitch is if you are casting a spell on a dying enemy, you sometimes get locked out of doing actions when you finish or interrupt the cast if the enemy dies before you get it off.

These are incredibly crippling bugs in a game that requires relatively fast reaction speed, they need to reconsider how the client and server checks how you chain your attacks together because the way it is right now losing an Aetherflow/Invigorate/Blunt Arrow heavily cripples you in a fight if it doesn't just outright wipe the party.

As a band-aid solution for the moment, give yourself a couple seconds (maybe 2) before you hit a cooldown next time.