The script prevents the downoad of the content

If I turn on NGINX on one of my subdomains, I do not download the contents of the server error pages (particular error 403)
When I look at the source code (Ctrl + U), I see that there is a script and links to images have incorrect links (see the screenshot)

Although 404 error loads the image normally

script:
/cdn-cgi/apps/head/E4zNL5fy0MBaO_2ysWnAmUJpMqE.js

PS. Is this a problem with me or CLOUDFLARE?

You have a relative path for the image, images/favicon_error.png is a relative path. I believe you want this to be absolute /images/favicon_error.png

example.com/path + images/favicon_error.pngexample.com/path/images/favicon_error.png
example.com/path + /images/favicon_error.pngexample.com/images/favicon_error.png

The fact is that the error 404 loads normally

And the error 403 even indicating the absolute path is the same