Weird Left-handed Sneak Attack Bug

[Dascedukan]

So I got this really strange visual glitch with my character's left arm when sneak attacking with a one handed weapon. I've never noticed it before and I really don't know what's causing it, any ideas?

 

Here's a link to a video I made showing off what I'm talking about: https://www.youtube.com/watch?v=_fRzv-32fPE (Load order provided in the description)

 

Thanks!