Hi there, long-time MP3Tag fan and first post.
Using: Mp3tag v3.11 / Win7-64
Problem: File > Export. If the destination path for the export file contains an apostrophe in the names, there is still an export file created but it is in the current default directory with filename "[SYNTAX ERROR IN FORMATTING STRING]".
The problem goes away if I remove the apostrophe from the target destination path.
Other aspects of MP3Tag (eg reading tags) function correctly when there are apostrophes in the file paths.
The work-around is to avoid having apostrophes in the path to an export destination, but nonetheless this is a bug and had me scratching my head for a while.