My client reported that when trying to create a new entry via the Control Panel, she had to add 1 paragraph at a time and keep resaving the entry. At a certain point, she couldn't add any more content to it, it would process the form, but the added content wasn't saved, and the system would show the homepage of the site (with the URL for the edit entry page).
The site is otherwise working fine. I thought it may be htaccess so I messed with a few things there, no change (and it doesn't make sense that this would be the problem in hindsight). I disabled all extensions via config override, that didn't change anything either. Checked the PHP and apache error logs, nothing there. Repaired and optimized db tables. Nothing.
EE 5.2.3 PHP 7.1.32