Comment 6 for bug 1183665

File names received from GList parameter in invoke_external_bulk_rename_utility are URL-encoded. Spaces in names replaced with '%20' literal.

Glib processes arguments and checks if for macro literals. It treats '%20' as macro '%2' and symbol '0'. So it filters out '%2' and leaves only zero.
E.g. 'file:///long%20directory/file%20name' will be translated to 'file:///long0directory/file0name'

One of the possible solutions is to URL-unescape file names.