File limit?

SanDisk MP3 players SanDisk® Clip Sport Go
2

The older versions of the Clip Sport player do not properly access filenames with 3-digit prefixes (or 3-digit track numbers).

Try using 2-digit numbering combined with minimal letter naming.

For example A01 - A99.  B01 - B99.  Etc

ALSO, try using FOLDER MODE.