I have the same hot tub (which I flippin' love BTW) and some times the diverter valve that controls the big foot jets can be noisy.
I find that turning off the pump before turning the valve helps because you can turn it all the way easier with the pump off.
You should be turning off the pump anyway before turning the valve as it's hard on the valve when turning it with all that water flowing.
I actually broke my other diverter valve last winter forcing it with the pump on. It was one of the coldest days of winter when it happened so the plastic part cracked at that temp and with that force of water on it. Incidentally my dealer was out to my house fixing it under warranty early Saturday morning after being called Friday evening. Pretty impressive