Drivers seat frame badly creaking and the seat back not holding position when left for a few hours.
So the frame of the seat has come under stress... to the point of cracking.

And the seat back has weakened in rigidity...

What do you get up to in your driver's seat Mr Steven?

(Is that not what the back seats are for?)
BTW the exhausts look cracking. Gives the rear end a nice bit of subtle aggression.