@Antonio > Again, the problem is not with your RX but the songs and possibly, as a result, the database. As requested, please post two or three of the problematic files.
If you could also please try converting the same M4A files to MP3, import those MP3s to rekordbox, then FORMAT your export USB drive, and export the MP3s to the USB drive. You only need to try a few tracks, not your entire library.
