Ash westbrook glitch

[Zetzumi]

I have battled ash westbrook twice and twice I have used knock off on acreus. Knock off does not remove the life orb. I know the ability Multitype prevents "The moves Covet, Knock Off, Switcheroo and Thief cannot remove Plates from a Pokémon with Multitype, but they can remove any other item. " the fact that the life orb can not be knocked off is a glitch. I unfortunately do not have photo evidence at this time. I will be sure to get it when I battle next week.