Was there an inordinate amount of sludge or metal in the pan when you changed it out? Skipping the TC leaves about 4 of the 8 liters in there. Did you use the correct ATF when you serviced it? How has it behaved for the last 20K?

On a side note, how old is your AMM (MAF)?

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280