I’ve found several instances of frames at the beginning or end of shots which are partially/fully duplicated from the frame beside it.
Two examples that come to mind are the shot of Luke climbing down the Falcon tunnel into the turret, and Luke running towards the burning homestead. For my project, in both cases I replaced the detail with the SSE.

The only reason I can think of for these oddities is damage on the negative, and nobody bothered to use an interpositive to replace the damaged frames.