that doesn't sound right. that would be like saying your car has a flat tire then pulling the motor out to fix the tire problem
abnormal noise is caused by mechanical interference or damaged mechanical parts.
The VAC Unit is a fully electronic device that controls the spindle. if the VAC Unit has any fault you would be seeing alarms on your screen. Since you see no alarms the VAC Unit must be ok.
I suggest you check the gearbox first then mechanical spindle components.