Hi
Have a fault on the nearside sliding door, started being hard to open. Took a punt and got a new door handle before I took it apart. Replaced it today but it turns out there is a fault with the locking mechanism that is rivetted to the door frame. Can't see anything obviously wrong with it, but when you pull the internal door handle it moves, but doesn't seem to be connected to any of the rods.

Is there a special name for the locking mechanism which is what the manuals call it, because I can't find hide nor hair of it on the web.
Thanks