Corrupt/Degraded .MTS Files with Ramdom Imbedded Footage

Howdy,

I shot AVCHD footage and saved the entire card (including private folder) onto a backup server. Months later I go to work with the footage in FCPX but encounter an error when importing the card. Using VLC I can watch the raw .MTS files, though they are choppy. What I notice is that the .MTS files actually have footage from a different shoot randomly imbedded and overwriting the footage that should be on the card. To be clear, a single .MTS file shows one person for the first few minutes then jump cuts to a different person recorded a week earlier and then jumps back again (multiple times). I have no idea how this is possible since, from my understanding, each .MTS file should be a single unique take.

I have tried repairing the .MTS files and viewing them in other players, but even when I manage to transcode the .MTS files, the result is a video with many sections overwritten with the wrong media.

Has anyone ever experienced a similar problem? Is there a solution? Or a way to avoid this problem in the future? If anyone wants to look at this wacky footage I can send you the raw .MTS file.

Thanks,
Dan