After talking with the knowledgeable Artbees support team, it looks like the problem is the combination of Firefox, Wordpress 4.9 and Wpbakery 5.1.1 is the problem.
But the situation is not fatal.
The solution is workable. I just need to use a different browser for now.
I have tested it with safari and it works. I haven’t tried chrome yet.
Hope that helps!