I'm not convinced that the new content collections is working as it should.
I'm working on a new site which involves 3 collections: songs, books, and songs-in-books. I can create a song, and display it on a page. I can create the book that song is in, and display it on a page. All good.
When I add the bookSong entry to bind the two together with a reference to book and a reference to song, I can no longer run "npm run dev", because apparently the book and/or the song no longer exist so I get "InvalidContentEntryDataError" (a new error in v5, I think)
Sometimes it works, sometimes it doesn't. Once I managed to get it to work by prefixing the bookSong file with an underscore, starting the server, then reverting the filename change.
I've solved the problem for myself by reverting to v4, where it all works fine (with a couple of minor changes needed in the astro files). But I thought the people working on v5 might find this a useful thing to test.