I am having the same issue, but I’ve narrowed my issue down to my theme’s core plugin. If I disable this plugin, the single event page loads. However, I can’t get ANY error messages no matter what I do. No errors in troubleshooting mode, WP debug mode, or the DevTools console.
This error only occurs when I have “Use updated calendar designs” enabled. The legacy single events page works just fine.
How should I proceed?