Today, I went under the car. The leak is from right rear part of the transmission.
Can this leak be due to the thing I mentioned in my first post in this thread: "According to Stu Ritter’s book, if the car is parked for a week or more, the ATF in the torque converter may drain back into the transmission housing. Then the ATF may run out of the front input seal."?

I did the wiping -> turn on/off -> wiping as described in my previous post:

http://www.peachparts.com/shopforum/diesel-discussion/205528-atf-slow-leak-above-pan-right-rear-easy-repair.html

ATF is coming out there.

Due to the leak there, the dealer did the following repair last October.

The invoice states "replace governor pressure valve replaced".
000-304-28-90 magneto supp
000-304-27-90 coil
115-304-01-60 seal.accel c
001-997-35-48 seal ring, tr
008-997-30-48 seal ring, vl
008-997-31-48 seal ring, vl

The dealer said that the leak looked like from the part 123 277 0103 in the picture, but it was from elsewhere.

I asked why the invoice mentions "governor pressure valve" while the parts list does not contain it. The dealer answered, "The magneto supp and coil that was replaced are part of what is called in Mercedes a Governor pressure valve switch. In modern days, it is also called solenoid."