I’m going to make a guess here that people with this issue are using guberbug gutenberg. No one included this information, so I am assuming.
This is a known issue using the wp block editor. This has been an issue with the new editor for quite some time. There are plenty of topics in this forum about this. I don’t see it being corrected any time soon.
If you select the category and update the post and then reload the page the correct custom fields should appear.
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