I can’t share an exact solution because I am not seeing any problems on any of my sites. The only thing I can really do here is make suggestions.
One major issue could be that you are using glutenberg. The version of ACF that you’re using still has issues with the new editor and this might cause some issues.
There have been other similar issues that have been fixed by reinstalling ACF. Delete it from your site and download it from your account and reinstall.
Updating from 4 to 5 can also cause issues. There is an upgrading guide here https://www.advancedcustomfields.com/resources/upgrade-guide-version-5/ and it includes some additional troubleshooting tips at the end, including a link to contact support.
You may have a conflict with another plugin. You can test this by deactivating the other plugins on the site to see if the problem goes away.
You might also have conflict with something in the theme. To test this you would need to see if the problem persists in another theme.
The version of ACF is working correctly if it has been updated successfully and there are no conflicts with theme or plugins.
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