When I copy or move a file in Nautilus the first time durring a session, the window reads just fine with the Orca screen reader. However, if I copy or move another file, Orca acts like there's nothing in the window.  If I restart Orca, sometimes the window becomes readable again. Other times, I have to reboot my computer to be able to read the window again.
Steps to reproduce.
1. start the screen reader by pressing alt super S.
2. Find a folder with a large number of files. The music folder will work if it has more than a gig of stuff. You want to use at least a gig of files to make sure that the file operations window appears.
3. Copy the files to another folder, such as an external drive. While the files are being copied, if you use flat review, you will hear things like progress and time remaining.
4. Copy the files back to where you got them from. This time, Orca will either say "blank" or "filler" when using flat review. If you get a window asking you if you want to replace files, Orca will read that part of the process just fine.