the_content(); erroneously closing off previous opening before it

the_content() is probably rendering a link ( or maybe your browser may be auto formatting one ).

You can test if this is so by instead of using the_content();

using

// Get the Content of the post 
$postContent = get_the_content();
// Escape all the HTML
$postContent =  htmlentities($postContent);
// Print it to screen and verify if any links are inside.
print_r($postContent);

if you have links in the content or expect them try simply replacing them like

// Get the Content of the post 
$postContent = get_the_content();
// some simple regex 
$postContent = preg_replace('/<a.+?>/','<strike>',$postContent);
// some more simple regex 
$postContent = preg_replace('/<\/a>/','</strike>',$postContent);
echo $postContent;

The above code will render all the links as strike through text you could replace this with underlines or even with a span that with the clever use of capture groups could be used to bind click events to said spans and you could still have functional links.

error code: 523