I am getting this a lot today when saving a pbix file in desktop. It just sits on this dialog and I have to kill power bi in task manager and recover lost file. I have latest version of the desktop app and file is quite big at around 140Mb.
All our pbix files are imported data. This particular file is now the biggest at about 140Mb with a lot of data and a lot of pages with numerous bookmarks. I have been using power bi intensively for 2 years now and it had never crashed/hung on me in this way before.
Maybe our files and complexity had not got to this point before and now it has I am seeing this behaviour.