Is it possible that the enemy's movement is framerate based? If you update the position every frame and the framerate is different in the build it will move faster or slower.
Yup, that makes complete sense. That's probably what it is.
You should multiply the movement with time.deltatime then or even better move it to FixedUpdate()
Well, I did do that, but there is probably some other mischief going on that I can't see.
