The scene changes occur on what are called glue frames or splices.

"Strips of footage would be hand cut and attached together with tape and then later in time, glue"

So it is glue, and partially at times, part of the next frame.

After each one, the next scene change would be spliced to it, in this case, the next shot is this:

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A cleaned up version:

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Alternate frame:

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So just think about how this cleanup has to be done, at times after every scene. That is why cropping it off, will be the best way to preserve the original shot.

Team Negative1