Oscar Contreras

Perfect!

@joyously that was a great suggestion from you! I checked the console and there was a problem with the jQuery library and some conflicts since I use loading one versión from Bootstrap CDN and the Customizer was trying with the wordpress’ default one.

The solution, was just to comment (or remove) the jQuery related to Bootstrap and just let it use the one loaded by WordPress itself. I already check and there seems to be no problem with the CSS library so far. Then now, I think this has been resolved.

Thanks.

Thanks for the replies to Jose and Joy. @jcastaneda No, I neither have any plugin active nor installed. I removed the ones that come by default with the fresh wordpress zip file.

@joyously , thanks for the suggestion, I tried after you posted it but unfortunately the Customize has not changed. I checked the inspector element in google chrome and the new div wraps the widget like it is supposed to do, so nothing odd about it and the class in it is widget_text since is a Widget Text as I mentioned on the main question.