Join Date: Jul 2007
Location: South Yorkshire
Possibly the built-in MP3 playback doesn't like low bitrate MP3s, or some of the MP3s were encoded using options that the audio unit doesn't like - maybe it doesn't like mono, for example.
It's always possible to re-encode MP3s on a PC using free programs like Audacity. That may fix the 'broken' MP3s. You will lose a bit of quality, but with an audiobook that's unlikely to be noticable.
That said, touch wood I've not found any MP3s that won't play in the Sony headunit in my C-Max.
2011 Grand C-Max Titanium