Found this via google search for the same problem - Just wanted to note the same fix works for current gen.
CSS for "upfront-editor-interface" needs to be set to not combine or minify and it will solve this problem
I figured out a workaround using a php text widget (which you will see), but I will grant access for you.
https://gwgh.com/category/investments is an example of a page where I want to use items from the data drag and drop to place the Name & category description.
I've experienced this as well, Hummingbird is the recommended solution, but even that has some render blocking scripts to make it work & i'm not entirely satisfied with how the page loads in chunks. I'm getting about a 3.5 second load time.
There's a section within hummingbird to do Gzip compression, which is where you can re-organize whether things load in the header or in the footer, which may solve the loading issue.