My 300TD is encrusted in ice right now or I would go out and take a picture.

So please excuse the cheesy graphics but if you squint real hard it starts to resemble a car...

Normally the seats are like this, if you were looking in from the right side of the car:

\__....\__

When you fold the back seat, the first step is to bring the bottom cushion up

\ |....\__

Then you remove the headrest and fold the backrest down flat

__|...\__

Now if you have the front seat too far back you will end up with this

__| \__

The back of the front seat pushes against the (now vertical) seat bottom cushion of the back seat. This in turn jams the (now horizontal) backrest of the back seat against the bottom of the back seat bottom cushion.

If you move the front seat forward slightly this relieves the pressure on the back seat parts and should let the back seat backrest rise up.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech