Mixed media type libraries are depreciated and "broken" according to the documentation[1], which is fair enough, but sometimes this results in weirdness if a TV-show is also part of a franchise and has associated TV-movies (e.g. the Battlestar Galactica reboot, Futurama, or Breaking Bad). If you want to keep those movies on your file system in a folder with the other stuff from the franchise, Jellyfin often can't handle it. And it's not obvious to new users whether these TV-movies belong in a TV-shows library or a movies library.

I've also noticed it cannot handle additional layers of folders (i.e. for Genres) in TV show libraries, but it can handle that layer in movie libraries. Failure mode (the "going nuts") looks like those genre folders recognized as bizarre or obscure television shows, and nothing scanned the next layer down.

I haven't looked into how their scanning algorithms work, but it's definitely frustrating that there's not a button or feature to say: "No, Jellyfin, this is a folder, not a show or movie. Try scanning again on the subtree starting here."

Honestly, any software that either silently/automatically reorganizes a user's files and folders (not Jellyfin, but there are others that do this... even FOSS projects) or demands a specific meta-hierarchy on the file system is frustrating to anyone who deliberately keeps their files and folders well-organized.

[1]: https://jellyfin.org/docs/general/server/media/mixed-movies-...