Common on those Dodge vans for the floor to rust out between the seat and gas pedal. That would allow the floor to move enough for the seal to come out. Other than that the seal shouldn't move unless the clamps are gone or the gasket was maybe damaged during service.
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2011 Ram 1500 Quad Cab, 4x4, 3.55, HEMI
2009 TL-32BHS Trail-Lite by R-Vision