Fun fact: although everything indicated that the problem was with ACF PRO, actually it was bad requests from Theme Options page for the theme we are using.
We have made a workaround for this, since the loading of that theme options was always happening and was consuming almost 5/7secs only for that, we though in removing it, putting a direct link in admin bar and the entire wp-admin is now really fast, although we have a LOT custom fields (probably more than 200) and a lot plugins, we could optimize the code in order to have loading times never superior to 2secs. 🙂
Uff, this was very celabrated here in my company! Hehe. 🙂
Thank you anyway.
