No issues with the seat other than I find myself leaning to the right for some reason...and I believe a seat with so many position options needs a memory setting.
The tilting to the right issue is also found in other vehicles, it's a safety issue. In a side impact, the tilting to the right helps remove the driver, or the tilting to the left for the passenger, away from the doors and impact. I have also experienced this "tilt" in many other vehicles, very uncomfortable for long drives. But I have not noticed this in my 5th gen. Could be because it is considered a truck and not a car. Different govt. rules.
I have leather seats installed by SE Toyota, non-Liquid-cell. (According to the window sticker). Whatever liquid-cell means. Could you folks have the liquid-cell issue causing the back pain even with the lumbar deflated? I too have a tender back but no issues with my leather seats. At least not yet! (I am getting older by the minute)! If so, I wonder if you can remove the liquidcell......just a thought.