After upgrading the WordPress core, the dashboard of my site is now incredibly slow. And by slow, I mean there is high latency after clicking on any of the menu items. For instance, after clicking on "Posts", it takes more than 30 seconds to load.
The actual front-end of the site loads at normal speeds, so the problem is isolated to the Dashboard.
I've tried setting up a fresh installation in a sub-folder on the same domain, imported all the posts + pages, activated the same plugins, and with this version the Dashboard is nice and fast.
After seeing that a fresh install is nice and fast, I switched the main site to use this new fresh database, but it's still slow! It boggles the mind!
I'm suspecting there are corrupt files somewhere in the core, or the plugin files are faulty. Is this possible?
Any other suggestions would be appreciated!