I have this issue as well. I just created a new field group with one WYSIWYG field. I added the group to my blog page, but when I type text in the ACF WYSIWYG editor and update the page, the editor is blank after the page refreshes (so my text is not saved).
I created a new page to test and for some reason was able to successfully save the custom field on that page. Somehow it seems to be specific to my Blog page, as if it has gotten corrupted or something? I don’t see any JS errors.
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