When editing a post on Wordpress, I am attempting to upload an image from the Edit post screen. a small Image icon opens the pane which gives me three options: Upload, Media Library, Insert from URL. it looks like this:
When I choose Upload, and choose an image, I get
Unfortunately, for me, this is caused by the upload endpoint returning bad content. it seems to return BOTH an HTML redirection notice (not a real redirect, just a notice telling the user the media has moved), and then it contains the JSON response AFTEr the close of the body tag.
see both pictures
Notice that after the redirection notification there's the JSON for the media that was just created.
I am on Wordpress 5.3.2 and I am using the "WP Offload Media Lite" plugin which might be related but in fact I saw the problem when the plugin was not installed so I think it might not be related.
I am using only a basic set of other plugins, like Akismet, Contact Form, Insert Headers & footers, and WP Mail SMTP. I have only a basic theme chosen (but I don't think that's the problem)
some answers I found on the internet
• this person suggests problems happen when your media filename have spaces
https://www.quora.com/How-do-I-solve-the-response-is-not-a-valid-JSON-response-in-WordPress
• This Wordpress support topic is closed for commenting and offers no solution other than use the Health check, which does me no good
https://wordpress.org/support/topic/the-response-is-not-a-valid-json-response-2/
• This non-developer WordPress user suggests some work-arounds which are simply to use the other way to upload media into your WordPress site:
https://navinrao.com/the-response-is-not-a-valid-json-response
these might be good answers but it seems to me the problem is a bug