Driver's seat issue

When sitting in the driver's seat, the right rear part sinks down further. Almost like something is broken. But I took the seat out this weekend and nothing seems broken or out of place. As you can see, the right side of the rear bar has more of a gap between it and the seat track. With the seat out and flipped upside down, you can push the right side track in, there's a lot of movement. Nothing seems broken or out of place. But I don't have anything to compare it to. The passenger seats seems different. I fastened a spacer made out if a piece of PVC board to take up that space, but I'd like to fix it correctly.
Any ideas? All of the photos are the rear underside of the seat.

Left side bar, very little space

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Right side bar, large gap

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View from outside the rail

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The spacer I made

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