Not sure how to disable that feature or how it seems to get enabled in the first place, but I've found a workaround that seems to increase the number of tracks pulled from.
1. Select "Browse"
2. Select "Songs" (not Artists, Albums or Others)
3. When the full list appears, select one of the songs.
4. When it returns to the main USB screen, make sure Random is selected and Repeat is not.
This should allow it to play random tracks from the whole list of songs. Let me know if this works for you or not.
Last edited by Shorty; 02-14-2018 at 08:55 AM.