Reat seat won't come out !

I have a 04 reg Ulysse, and have recently had an "insertion error" on one of the rear row of seats, and it got stuck with the rear runners in place and the front ones not. I wasn't able to remove the seat at all, but have now managed to get it correctly located, and it slides back and forwards correctly.

BUT.. it now won't come out. Flipping the seat back forward doesn't release the rear runners, and the bar across the bottom, that would normally release them, doesn't.

Any ideas of how I, or even a FIAT dealer, might be able to fix this ?

I had it once and they needed to change a cable (they call it "rod") inside the seat.

There is another cross bar under the rear part of the seat which you can use to fold it after you had folded the backrest.

Then you can check if that cable is broken or just came out of its eyelet.

You can see it, no. 18 here:
The rear cross bar can also be seen as a part of no. 3