JSON Parse error: Unrecognized token

I am getting this error upon trying to add a new post or copying a post with certain text in the body. See the attached picture. When the post has the {audio...} text or something else in this line, the error shows up. Interestingly, the post still is applied and works but trying to understand what this error is and how to eliminate it.

In previous versions (v 3.x) this was not a problem. I just updated to the latest version 5.0.36 and this error started showing up. Let me know how to resolve this.

Thanks for your reply