Hi
I posted a message on 13/6 about this problem.
The problem was resolved when MB UK changed the transmission fluid plus all the seals etc. It was a costly exercise for what was just a fluid change - seems the fluid is very expensive here in the UK and MB labour charges the same. At least they did know what they were doing and i was just pleased that the problem was sorted without delving into the mysteries of the gearbox itself. They did say the fluid level was down a bit - that was apparently enough to cause the symptoms.
No problem since and had some use this year - summer finally came to the UK in July
Good Luck