Sounds like the cable is binding. I personally would replace the regulator. There are other wear items besides the clips. I just find it a PITA to do the clips as well. Mr.BMW has a Video DIY on how he has the clip stay in place. Looks like he used 12 or 14 GA wire to sinch the clip in place.
My $.02, replace the regulator.

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2011 E70 50i M Sport