It's the grease inside it open it up if you don't believe me
It's very sticky grease that crackles as the cogs unmesh even if you spray coppers lip in there it still makes a noise that's what I did and it made no difference at all nothing to be concerned about its NORMAL
This is plastic parts unmeshing and not an electrical problem you are all reading too much into it take the 4 screws out and open it have a look then chill out !!!
I didn't hear it at all until I removed the ais off mine I guess everyone is just more sensative to it cos now you can hear it it must be fooked well it's not
My exup works very well and yes it crackles from the servo it ain't broke and it dont need fixing you will waste your money trying to silence it