Annoying knock sound under driver's seat: 2012 650i xDrive Coupe

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There is an annoying clicking or knocking sound made by my driver's seat when turning or even accelerating/decelerating. The seat seems like it makes a very slight shift during the sound. I took it to my local BMW dealership for the fix about 3 weeks ago, and they replaced a few parts under the seat and called it good.
This did not work, in fact might have made it a little worse. Anyone else have this problem? The sound almost sounds like it is coming from inside the door, but I can recreate the sound by manually shifting my weight around in the seat while holding on to it.
I made another appointment. We will see what they can do.