An app block disappeared from our production store and our development store since yesterday for no apparent reason. The production store had it installed through our public app, and the dev store through another (development) app. No changes were made to the block’s code or configuration since it last worked.
Going to the theme editor, it was absent from the page where it had been installed and working stably until now. Re-adding it fixed the issue.
Checkout UI extensions installed via the same app are fortunately still working, otherwise it would have been catastrophic.
What could be the reason?