The playback order resets during shuffle playback.

If one of the following situations occurs during shuffle playback, the playback order will reset.
 
Situations in which playback order information resets:

• When you connect the Walkman to a computer to update the database.
  NOTE: You can continue playback of the track that you were playing at the time.
• When you remove and reinsert an SD card to update the database.
  NOTE: You can continue playback of the track that you were playing at the time.
• When you turn the Walkman off.
• When the battery is completely depleted and the Walkman turns off.