yeah, unfortunately, the assessment that the clips are similar lengths / timecode, etc. didn’t seem to play out.
the issue arose when I was syncing things using plural eyes – and when I originally went to open the new timelines in fcpx, it claimed the footage was already in that particular library, so I had to create new libraries to import them into. This would work, and everything would look great, but then when I went to move them to the library I wanted to bring them into it would occasionally tell me the footage already existed, or worse, move it but then many of the clips were subbed out with the wrong file, no error warnings or anything…