I have now tried to deactivate and activate all plugins in different configuration. I’ve even tried deactivating “Vision Core” and the “Page Builder” plugin. And I don’t have that many. It’s still a site in development.
What I’ve found is that when I deactivate “Vision Core” the code starting with “#vision-testimonials_5b7cfb46d2812” is replaced by the shortcode starting with “[vision_testimonials_ctn]”.
In any other configuration the code starting with “#vision-testimonials_5b7cfb46d2812” is still there.
So my conclusion is that this is an error in the Vision Core plugin and the Testimonials element?