It's unclear to me how to fix this. The mechanic has no idea either (wants me to book it in, struggling to find opportunity to leave it with them for the day).
If anyone's had to fiddle with these before i'd appreciate any insights. There's some strappy stuff that runs down inside the seat (the catch is a pull-strap in the seat, beside the headrest holes) and it looks like a loop is meant to be caught on something and it no longer is. But hard to be sure as visibility is difficult, and comparing to the one that works it almost seems like the catch is within the hinge area itself.
I don't want to destroy the seat to fix it.
I can't blame the mechanic as I hadnt folded that seat up in probably a year, so it could've failed at any time prior. But now i'm annoyed because I can't carry bulky items in the boot of my car

Cheers in advance.
BJ