Sometimes, we see the rook or the UB doing his melee attack. While the animation of attacking does complete, the hit is actually not done.
Rook have this problem ans some time he does 1/2 attack animation then again a 1/2 attack animation.
With UB ive seen this mostly happen when you warp near an ennemy and then you clearly see the UB giving a hit on the target but there is no damage / evade or whatever..