Inherit velocity in shuriken particle system goes haywire in build version

Hi, I am using a particle system for showing some projectile scatter from the end of a gun when fired. I have set the Inherit Velocity to 0.75 (don't want to inherit full velocity as the effect just looks nicer this way) and while in the unity environment it works perfectly.

However, when I build the version for windows and run it, the effect goes mad, it drags the particles out incredibly fast (even when player is moving slowly) and seems to project them in any direction other than the one the player is facing.

Anyone got any idea why this might be?

I am calling the Emit in FixedUpdate so as to always have a steady stream that doesn't fluctuate with framerate.