[twindman]

I had the old REAL frame flex in my 2006. This is in the area at the front where the frame goes up, then forward again. The joints in the angles break and then the front will move up and down depending on whether the camper is on jacks or the truck.

From what I understand, the new flex is around the front slides and cracks show up on the side near the corner of the slide opening. Same principle but not on such a serious nature as the whole front end flopping around.
I also had flex on my 2013 Mountaineer. Not quite as bad at the front end. At the same time the studs at the rear near the bottom had broken loose which somehow allowed the back wall to slightly separate from the sidewalls.
So yes, flex has been around for a long time.