Bumping this old thread with the 20/20 hindsight that comes from the passage of five years since the post and having just fixed this problem and done a YouTube video on the repair.

Yes, the 722.9's had a set of consistent problems, and resulted as usual in a class action suit when MB denied knowledge of any failure pattern (Mercedes named in class action lawsuit over defect in the 722.9 7G-Tronic automatic transmission | Got a Class Action?) but the problem of the transmissions shutting down the controller (with no Check Engine Light) was well established, and the cause was failed conductor plates, just like their 722.6 predecessor. It would have been an easy fix if MB hadn't *coded* the replacement plate (has to be coded in with a STAR machine), and refused to sell the parts over the counter or to independents, citing it as a "theft part" to get around Right to Repair laws, guaranteeing your only option was... pay the dealer the $2,500 to $3,500.

The market has adapted, and the situation has improved, and I am now living proof that...

1. There are many suppliers who will fix your actual bad conductor plate for $200 to $250 so no recoding is necessary
2. It takes just a messy half day to pull and replace the valve body and remove the plate (although the car is down while waiting for repair at the vendor)
3. You can clear the code with an Autel scanner

...because I did it and have the YouTube video to prove it...

https://youtu.be/gpkkEySV6ZE