Long standing Vi bug
Ever since the introduction of trinkets, theres been a bug with vi. While charging vault breaker if you place a trinket, the skill acts as if you were cced; the ability is cancelled, half the mana refunded, and cooldown set to 3 seconds.
Ive already submitted a ticket so please dont recommend that :) A video example of the bug can be found here! The video seems to be bugged out in high definition, anyways just pay attention to the mana bar and vault breaker cooldown.