CharacterController.move is jerky in coroutine

Thanks to Bunny83 and Bérenger Mantoue, I'm using a coUpdate every 0.1 seconds to control my AI script, which has boosted my performance brilliantly. Unfortunately, my zombies (with CharacterController attached) now jerk forward, as the move command is only being called every o.1 seconds. Am I missing something?

the relevant code is:

 function Start()
 {
     CoUpdate();
 }
  
 function CoUpdate()
 {
     while(true)
     {
         controller.Move(forward * Time.deltaTime * speed);
         yield new WaitForSeconds(0.1);
     }
 }

Any way I can get them moving forward smoothly again please? Any help appreciated. Cheers Ian