I’ve noticed the back plate snapping off and making a noise which I at first thought was a suspension problem. But it ended up being this piece disconnecting or snapping off the base. It took a while for me to correlate the two.
It seems to only happen on hard bumps or turns and it’s hardly replicable on the spot.
The pic was the only thing I found via search but my hooks do not appear damaged

 

Just to clarify. I would see my seat back disconnected and just pushed it back in to place. This was all very causally until I checked back seat(everything normal) and less than a mile later heard noise and reached around and it was detached so I can’t 100% say it’s the source but I’m confident so we shall see.

 

Even if your hooks aren’t broken they could still be the problem. Maybe they are less stiff then they used to be because of age. Is there any way to compare their stiffness to the passenger side seat hooks which presumably hold everything in place. Worth considering if you haven’t already.