On a regular basis, the sub pages on this site return a 500 error.
Investigation shows that the rewrite rules in .htaccess have been changed and the site is looking for content in /es/. But /es/ doesn't exist.
Changing the rules in .htaccess (see attached) or resaving the permalinks fixes the issue immediately. But it keeps reoccurring and the client is losing faith.
It appears to be WPML related because it is the rewrite rules relating to languages that are being changed.
Thank you for contacting WPML Support, I will be happy to help you today.
This this issue actually comes from certain third-party plugins calling flush_rewrite_rules(true) function too often. This causes WordPress to overwrite .htaccess.