We use
TagLib as our MP3 ID3 tag parser. It's a robust and well-tested library; as noted under "Projects Using TagLib" it's also used by a number of high-profile projects like the Amazon Kindle, last.fm, VLC, and others.
Unfortunately this problem appears to be a bug in TagLib, so it's not something we have direct control over. We have seen it manifest with a few rare MP3s and seems to have something to do with how those MP3s were encoded. Re-encoding the MP3 fixes it, so I'm guessing it's the result of a glitch in a particular encoder.
Aside from the obvious cosmetic problem it poses, it has no other impact in Centova Cast so it shouldn't be a cause for concern. We regularly update TagLib as they release new versions so as soon as they fix the issue, it will also be resolved in Centova Cast.