Bench seat issue

[rs74]

I recently took the bench out of my old short bed cab and swapped it into my K30. I jumped into it yesterday and when I sat against the back it moved back a couple inches. Not the whole seat just the back part of the seat.So I got back out and pushed on the back and you can push it back a couple of inches before it stops. I checked two of my other seats and they don't do this. When they are back they don't move at all.

When the backs are all the way back the side hinge rest againt a pin I think. So I am starting to wonder if this seat back is sprung or something. I hope all this makes since. If nothing else I will have to try and put up a video of this. I just don't like how it moves back when you set against it. It should be solid when you first set back on it with no movement.