Rear mech inner replaced

Hi folks.
Just got my bike back from a service, and one of the things they have done is replace the rear mech inner.
Can anyone tell me why they would do this?
What kind of symptoms would that issue have been causing pre-replacement?
Thanks
Just got my bike back from a service, and one of the things they have done is replace the rear mech inner.
Can anyone tell me why they would do this?
What kind of symptoms would that issue have been causing pre-replacement?
Thanks
0
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