Hello, @mediamacs,
I just want to add here. I checked your page content shortcode of WPbakery page builder in the code mode. It seems that there was an issue with the shortcode, for example, column close shortcodes were not there, WPbakery Text element shortcodes were replaced by [text_output]. I went ahead and edited all the shortcodes now the page is working fine in the backend.
Please check your page. Please the page URL and screenshot in the secure note.
Thanks