If your site became slower (in front-end and back-end), if you can’t use customizer or changes made with page builders doesn’t take effect (or even broke the page), please check number of revisions on your site.
WordPress creates a lot of revisions when you are writing. If you aren’t careful you can end up with thousands of unnecessary revisions in your database.
More details regarding revisions: https://codex.wordpress.org/Revisions
Our recommendation is to limit number of revisions (default is unlimited) and to decrease autosave interval (default is 60 seconds). So, please follow these instructions:
1. open wp-config.php
2. add this into the file
define('AUTOSAVE_INTERVAL', 300); // seconds
define('WP_POST_REVISIONS', 3);
if you want to limit number of revisions or
2a. add this into the file:
define('AUTOSAVE_INTERVAL', 300); // seconds
define('WP_POST_REVISIONS', false);
if you want to completely disable this feature.
NOTE: in both cases we've used 5 minutes (300 seconds) for autosave interval, but you can change it to fit your needs.
If you already have many revisions on your site, then please optimize database (clean old revisions). We strongly recommend to use free WP-Optimize plugin for this purpose.