Final Cut Pro re-link error

Final Cut 10.5.4.

For the purpose of exporting to Resolve for color correction, I need to re-wrap some video files from a Sony camera from .mp4 to .mov. No problem, I used Cineplay and did this fine.

So I took "video.mp4" and used Cineplay to turn it into "video.mov" without any transcoding.

Then I open FCP to re-link the files.

Half of the 12-files re-linked without error. The other are giving me an error "The New File is not long enough to cover clip "video.mp4" in project ..."

But the clips are the same length. Any idea why this might be happening with some files and not with others, when the workflow is identical for all of them?