What a pity. A few years ago, they were ok. Not perfect but ok. The front wing ones were a bit too short and the stop piece at the rear of the door piece was too long, preventing the pin from entering the hole in the door. So I had to knock the alu locking piece in the groove out a bit, and saw it off, then file and push back. But the rear ones were ok, not like what you describe here. There is just one supplier, guaranteed, and BMW need to know about this.
i bought my trims from BMW a few years ago (i think 2012 or 2013) ... exactly like the pics earlier within this thread ... way different than the original trim on my coupe. because i wasn't ready to try to put them on my car at that time, i am probably stuck with a couple of hundred dollars worth of new junk. i like the idea of giving the guys from BMW a rear fender and a new rear belt trim and see how long it takes them to put it on ... i would even donate one of these belt trims