So I am going to respectfully disagree. Tranny oil behind the passenger floorboard where the TCM sits is actually a quite common issue with M112/M113 engines. The transmission fluid essentially travels up the wiring harness, which soaks up the fluid. The culprit is a connector, under the car (see the above video) that start leaking fluid as the O-ring has become brittle.
I recently got a TCU tune and went to change out my TCU and notices tranny fluid on the TCU and also around it.

Here are a couple of threads from MBworld explaining just that.

https://mbworld.org/forums/sl55-amg-...dule-help.html
https://mbworld.org/forums/c32-amg-c...-over-tcu.html

My car only has 25,000 miles on it but my guess is with age most of those plugs start leaking if they are never replaced (they should be replaced with every transmission service). Most of us might never notice it unless it becomes so bad as to leak fluid on the garage floor and/or fluid pushes into the TCU module and will cause all sorts of issues with shifting/limp mode etc.
If you want to find out, remove the carpet in the passenger side, pull back the foam and unscrew the three screws that hold in the metal backing plate to see what it looks like behind there.

All that being said, that problem would not lead to OP's problem with the but he might still have that leak if the connector has never been replaced so I would tackle that as well.