It's a bad design: the glass lifter (elevator) is a metal bracket which bolted to the glass, but it has plastic molding to hold the steel cable ends, and the weak-link plastic cracked then broke, leading to loose cable and a dead window regulator. Why they didn't make the elevator 100% metal? Assembly issue: it's impossible to assemble the metal elevator to the guide rails. Of course the elevator can be 100% metal but the design will need more assembly time.I see that the drivers side has been replaced three times on my car.
Another alternative is buying used from a salvage car. It can be questionable in terms of what you're getting and is extra work to remove it from the junk car, but you can usually find a good genuine BMW part for around $20. Judging by the number of cars I see with removed door panels it seems to be a popular part to grab at the pick n pull.I would suggest OEM ones, but then I went and looked and holy crap, they are almost $500 from FCP Euro.
Honestly, I'd go pick something under the "standard replacement" category on RockAuto
The plastic part that snaps into the vertical guide rail has to be flexible (why it's made plastic) and a new designed metal part will not be able to snap on the rail. The design has to be changed in order to use 100% metal elevator.Maybe somebody could 3D print metal parts to replace the plastic crap.