Driver seat belt issue 1991 wagon

Hey guys, wanted to see if anybody had the same problem I’m having. I have a 91 wagon and the driver side front seat belt moves back-and-forth while I’m driving. So far I’ve replaced the small L-shaped mechanism that the door pushes when closed. I have also replaced a small box underneath the driver side seat and the problem remains. I have also replaced the entire mechanical seatbelt mechanism with no success. If anyone’s had the same issue please chime in, thanks in events.