I thought I was developing a full-stack application with Next.js, but I wasn't. There were settings to add images and videos in the administration panel. In development mode, these features work without any problems, but in production mode, images and videos added later do not work. So they are not shown in the browser. It is necessary to restart the project. You need a 3rd party service or an additional backend structure for image and video upload.

So we can say that Next.js ≠ Full Stack application.