Gamplay; Yi weirdness

just had a game with yi and alpha strike was acting really weird. mostly not hitting all its targets if i issued a move command while i was untargetable (hitting one thing instead of four of the six things in range). also noticed that after one alpha strike i hit a brand four times with my auto attack (i was not blinded) and i even heard the sfx of a hit but he took no damage. it was a hot moment so i can't remember if i got an auto to damage before my next alpha strike or not. but i do distinctly remember the sound of four on hits without a change in brands health. also had ult and youmuu's active if that matters