Hello @santos,
Thanks for asking. 
- Ensure you are fully up to date. See our changelog.
- Clear all caches including browser cache then deactivate your caching plugins and other optimization plugins.
- If you’re using a CDN, please clear the CDN’s cache and disable optimization services.
- Test for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
- Remove custom CSS, Javascript and templates.
- Reset your htaccess file by renaming it to .htaccess-bak. Then in WP Admin Menu, go to Settings > Permalinks and just click the Save Changes button.
- Ensure that you are runing the recomended PHP version. As of now the suggested version is 7.0. You can refer following documented for more information. https://wordpress.org/about/requirements/
- PHP Max execution time we recommend at least 120 seconds or higher
- Contact your host to increase your allocated memory or do it yourself by adding this code in your
wp-config.php
define( 'WP_MEMORY_LIMIT', '256M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
If nothing helps, please give us WP Admin and FTP access in a Secure Note.
Thanks.