Scalability Pro Tables
I'm experiencing some very unexpected behaviour and I don't really understand how it's happened and wondered if Scalability Pro could have added some stuff to the database causing things to be dupliated and not created properly (like new brands, editorial tags etc). I've disabled all the plugins cleaned out as much as possible, but the issue still persists.
Scalability Pro does not add anything to your tables, but it does alter queries depending on which options you have enabled in the settings pages.
I recommend you disable the option for ‘remove sorting’ and test again and the remove LEFT JOIN to swap with EXISTS option too then test again.