Going through the tests, I noticed that ocf-filename-character-forbidden-error generates this error:

ERROR(PKG-009): .\ocf-filename-character-forbidden-error.epub/EPUB/nav_{}.xhtml(-1,-1): File name contains characters that are not allowed in OCF file names: ""{","}"".

But of all the characters banned by the epub specification, braces aren't in the list. Even OCF 2 appears to allow them.