Guns falling out of my hands

I have an odd glitch where my left hand only is unable to keep a hold of the guns. I think its unlikely to be related to the oculus rift touch controller as all other games work completely fine (robo recall/ tiltbrush etc).



And its only with my left hand. i grab a gun and after half a second or so my character drops it even though the in game hand is clenched.



Whats going on?