Enfold text editor text shows white in the text box so it can't be read

My issue is the same as the one below but the topic is closed and I don’t have a definitive solution:

“The description of the problem is easy : it suddenly became impossible to edit text. Text block in Avia layout builder is just white, I can’t do anything as there is not even a text cursor. The problem is the same for the normal WordPress editor (Visual). However it works when I pass from “Visual” to “Text”, but then I just get the html possibilities of course.

I deactivated all plugins and it didn’t help. When I switch to default theme Twenty thirteen, the problem is fixed, it’s working normally.

That’s quite a handicap and I would like to know what can be done to have the text editor working properly ?”

Best,
Jim