I hope you don’t mind if I post something here, even though this is showing resolved, just in case someone can use the info. I had the same JSON issue for awhile. For those using WordPress…I talked to WordPress support, since this message didn’t show up until I started using Gutenberg, or the Block Editor, and they narrowed it down to the firewall allowing some things through but not others. Their fix was to whitelist the files not coming through. No more JSON error messages. Not sure how they found those files not coming through. That is above my skillset. 🙂
I am wondering the same. Thank you for posting this important question.
