My thought on the mechanism is something has made it wear oddly in the first place.
Have a look at www.realoem.com it's a BMW parts list put the last 7 digits of your Vin into the search box and it will bring up your model then search for the part it gives exploded drawings and part numbers helps to make sure it will fit.
Also www.newtis.info it's a BMW technical information site as used by Dealers good for how too's etc
Dave