Why do I have to re-run ffindex every time I plug my external hard drive...

[Katie Boundary]

...into a new computer?

This would make sense if the computers assigned different letters to the drive, but that's not happening here.

[wonkey_monkey]

If it was anyone else, I'd guess it was mismatching FFmpeg versions. Luckily KB has me blocked so they won't see this answer and get in a strop because it turns out to be something completely different than no-one could possibly have guessed.