Some of the Shades abilities will be double cast when it uses them, except the double will have no visuals, or sound, and will have less gap in between the hits, making it impossible to dodge them. I don’t have a list of abilities, because it’s incredibly hard to work out which its doing it on, but it mostly happens during void+blood shades.
(If I had to guess its the void rings, and the blood orbs being invisible and weird)