v3 metadata edits only save with Ctrl+Enter, the save button does nothing until then

In the v3 beta the save button in the book editor works only sometimes. Editing tags does nothing when I click save. Opening the full-page view shows an empty publication date and throws an error popup even though I only touched tags. If I save once with Ctrl+Enter it goes through, the publication date reappears, and from then on every tag edit saves normally with either the button or the keyboard. Same behavior in the side panel view, except the error popup doesn't appear there.

Resolution: This is a publication-date validation problem, not a tags problem: the form loads with an empty/invalid pubdate, so the submit handler rejects the whole payload and the save button silently no-ops. The workaround is exactly the sequence above - press Ctrl+Enter once, which forces the submit and repopulates the publication date, after which the form validates and normal saves work for the rest of the session. A related symptom is a save failing with an "expected string but received date"-style error when updating a cover image whose filename is a long random string; renaming the image file to something simple lets it save. Most pubdate edge cases were fixed across the v3 betas but at least one remained, so stay on the latest beta.