Stanimir,
I’m at the point where I can’t keep 5.1.3 enabled. The page builder is only part of the problem. When I enable the plugin I am getting js conflicts on the homepage with Revolution Slider, and images are loading incredibly slow. I have done some testing on different computers, tried Safari and Chrome (different problems on each). Something is really causing a major slowdown.
I tried Siteground directly using a ticket, but they just send me back a gtmetrix report and some annoying boilerplate text.
My website just does not behave with 5.1.3 enabled. I wish I had access to 5.1.2 again to see if that the latest version truly is the issue.