I am getting this error “Updating failed. The response is not a valid JSON response.” every time I am saving a page in content Block Editor. I have a couple of ACF Blocks I am using, how do I debug this? I have set WP_DEBUG = true, but there really isn’t any useful feedback in the Console/Network developer tools, that will tell me where the problem is.
It looks like it has something to with the acf_register_block_type function and therender_template that is used. I have an <header> HTML tag in the template file, that it doesn’t seem to like. When I change it to a <div> tag, then no error.
I am experiencing the same on two websites. Yes, as Vayu said, it does look like it’s <header> tags are indeed breaking the json when I view the response in the network developer tools.
This is awesome , thanks.
