I have also read some cars when had tunes or maps installed on them, it can have an affect on the gear shifting smoothness of the car. Including TCU update.
If I were you purchasing a car of such quality, I would get the car up to temp, then test all Gear box modes. Give the car a good test drive. The MCT is never going to be as smooth as a 5g or 7g torque converter box especially that one in your S211 E63. But overall is a fantastic box. With its different options available. Changes are more firm in S+ and M mode going up and down the box. As said in a previous post, C mode the car stats off in 2nd gear for a more sedate pull away. S S+ M revert to 1st gear for a more sportier pull away. Also in C mode when say coasting to a round about, if you are in 2 gear and apply quick throttle the car can get mixed signals and can sometimes drop into 1st, as it gets slightly confused and believes you need more power. It takes a little getting used to the MCT. Its great fun at the same time. The only other little glitch with the MCT I find is when stationery at a junction and in C mode, there is a very ever so slight delay with pressing the accelerator and the car moving off, this is the carracter of the box, you do get used to it. It's not as noticeable in S S+ and manual mode.
Good luck finding your new to you M157 badgx
Forgot to add, I have a sprint booster installed on the car. This has changed to carracter of the box also. It definitely has sharpened up the carracter of the car. In c mode with sport option number 5 it's perfect for me. Race 10 and in M mode is neck breaking
it's fun when you're in the mood.