It might be possible to list out the files (list-current-files) in the backups and iterate through them while specifying the filename to the --file-to-restore argument using a script for files that can't be restored in a specific directory without this error.
I have this problem during verify as well. I can work around this by specifying subdirectories, for example,
ubuntu@ ubuntu: /media/ 1b[...snip. ..]a1/home/ chris$ duplicity --verbosity info --file-to-restore "Documents/" --archive-dir /media/ CHFOO_FAT32/ backups/ duplicity- cache/ verify file:// /media/ CHFOO_FAT32/ backups/ backups- laptop/ Documents/
It might be possible to list out the files (list-current- files) in the backups and iterate through them while specifying the filename to the --file-to-restore argument using a script for files that can't be restored in a specific directory without this error.