[GAMEPLAY] Caitlyn's r [Ace in the Hole] bug?

in the game, Caitlyn's ult goes into full cd but does no damage, when master yi uses his q. not sure the ability is cancelled during casting or during the traveling time. if it is cancelled during casting, shouldn't it be in partial cd instead of full cd? if it is cancelled during the traveling time, why master yi did not receive any damage? isn't his q [Alpha Strike] only becomes untargetable? not Invulnerability?