Could it be from the widescreen to pan-n-scan conversion?
I don't think it's video related, the scrape lines are also seen on actual 35mm release prints. Being white my guess is that they were either introduced on the camera negative or internegative.
Maybe someone with more knowledge about film could chime in and help explain why this early 80's print used for Star Wars home video looks like it does (large glue marks on almost every single cut) Does Star Wars being an A-B cut negative have something to do with it? It sort of looks like a 16mm film where they didn't use the "checkerboard" pattern, where you're alternating scenes back and forth on the A and B roll in order to make invisible splices.