The electric connector needs to make good solid contact. The original orings did not hold up. You need to have a new plug with the correct orings to control the leaking fluid. As you mentioned yours was leaking badly you should lift the carpet remove the styrofoam and the steel plate ( In the USA that is at the passengers feet) and check you Transmission Control Module (TCU). It has been reported that oil can whisk up the wiring harness to the TCU and cause damage.

The fluid looks really dirty. It could have caused sticky solenoids; Only changing the conductor plate will tell if that will fix the problem and putting new clean fluid in along with the conductor plate. I'm sure the fluid you have in the transmission now by flushing through your system has picked up a lot of dirt. Best to replace with new fluid: MB approval 236.14

Wish I could be more definitive, but without further testing with DRB III on N2 and N3 speed sensor and wiring harnesses it is not possible. A good transmission shop should be able to help. Should it be found your clutch packs are damaged it could be less expensive to buy a used transmission rather than repairing yours.

Good Luck!

PS it doesn't hurt to put a magnet in the fluid pan. Mercedes sells them.