I'm having this issue as well.
I've created 3 custom fields for custom post type Portfolio.
In the back-end of the post, I enter the info into the fields, click update. Refresh the page, the fields are empty.
What could be the problem?
WP 6.2.2
Meta Box Version 5.7.3 by MetaBox.io | Auto-updates disabled
Meta Box AIO Version 1.21.2 by MetaBox.io | Auto-updates disabled
WPCodeBox Version 1.4.1