3rd person controller glitch

I am using the Third person controller script that comes in the standard assets of Unity and when I try to move the player backwards, it flickers back and forth two ways, then rotates 180 degress and moves forward while continuously moving slightly left then slightly right quickly, but it is certainly not moving backwards. Why is this happening? Am I doing something wrong or is this the script's problem?

EDIT:It sets a variable called "movingBack" to true when your motion is negative, calls the variable to return a true/false in a function, but never uses the variable or function otherwise. It says in the comment over the variable "movingBack" call "Are we moving backwards (This locks the camera to not do a 180 degree spin)", but I don't see anywhere where anything actually locks the camera not to do this. How would I add this in?