Getting an old backup, from an ante-UTF-8 era, I found out many files had filenames with some characters unreadable, or partly readable depending on the software.
I tried my urlize script first but unac (that it depends on) failed with:
unac_string: Invalid or incomplete multibyte or wide character
The easiest way to get rid of these is simply use iconv, for instance doing in a directory with such files:
for file in *; do mv "$file" "`echo "$file" | iconv -f utf8 -c -t ascii//IGNORE`"; done