For me a quicker way to find which servo is buzzing is to grab my mechanic's stethoscope and touch each servo and the guilty one will will be found with ease. If you don't have a stethoscope, a long thin screwdriver will also work. Hold the screwdriver handle up to and touching your ear while you touch each servo with the blade end of the screwdriver. The vibration will transfer up the screwdriver shaft and buzz in your ear. Old race car mechanics trick.