Thanks for the quick reply. I've disabled my current Kadence theme and disabled the plugin of WpVivid staging. The only plugins active are now of Metabox. And I'm running the latest WordPress install 5.7.
I did the test again, and although now it works better with the Editor option disabled. However, when I enable it, it still not works as expected. It still doesn't show some fields. See the recording: https://share.getcloudapp.com/geu46D6b
I'll check my other MB view issue and will get back to you on that too.
Kind regards, Henri