Okay, so I just spent a lot of time testing.
I made a new SkeletonAnimation testing the animation - didn't have the bug.
I ripped out my SkeletonAnimation from my bugged object and tested the animation by itself with no other scripts - had the bug.
I made a new SkeletonAnimation, Inserted the scripts onto it and put it back into my Player gameobject
Tested the animation - no bugs.
I literally have no clue, the SkeletonAnimation component was bugged somehow and was a freak occurrence I guess (Possible a unity bug?). Luckily it was an easy fix, just remake the object.
thanks for your help