full close loop axis controller

Hi

i am using my b axis on mill-turn machine with servo motor feedback and works fine

but some mechanical error i am not able to eliminate

so i connect external encoder
now i want to know how to use external feedback

my b axis servo motor is same for milling spindle and b axis

so i need to change b axis command and spindle rpm command with mux2 component

but when i try to connect external encoder on b axis motor run away

i try to change direction but external feedback not working

i use b axis pid enable signal when i use motor as b axis

otherwise i use spindle command in mux2.0

but all time my b axis run away

i am using ethercat servo drive lsis make (korean)

thanks