The early 1997 722.6 had problems. I believe cars produced late in the year had an upgraded transmission.
I had my 97 E420 checked by the dealer (produced October 1997 - so one of the very last ones) and they said that it had the upgraded valve body, they also claim they upgraded the software (but it think that a bunch of c..p).

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2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)