Hi,
I had the same problem before, but I cant solve it this time using the same solution.
I have created a new portfolio item by cloning the last item. The last item uses the full width template, but after cloning the new item does not and I am not able to select any other template.
I have switched between child theme (which was marked as corrupted, as the style.css was empty) and main x-theme but still don’t have the selector on the right side when editing post in wordpress editor.
Could you look into it, please?