Recently I noticed that my admin dashboard for the posts listing (wp-admin/edit.php) was taking much longer than usual to load, sometimes close to 30 seconds if I had 20 posts listed. Also, I encountered an issue on the dashboard page for editing the Menu (wp-admin/nav-menus.php) where any time I hit Save it would hang indefinitely, eating up my server's RAM and maxing out the CPU until it timed out after about 300 seconds. The rest of the site and the other dashboard pages worked fine.
Upon investigating recent updates I temporarily deactivated the SmartCrawl plugin and sure enough these issues went away. I've granted support access to my site so you guys can investigate the latest SmartCrawl update. Hope this helps with troubleshooting!