The SansaZip does have several firmware bugs.
When pressing the play button while the starting animation is still showing the player will start playback as soon as as the animation is completed. But sometimes (most likely depending on the moment one presses play) the player then misbehaves (tested with audiobooks). When pressing the pause/play button the player will show the pause icon but will NOT interrupt playback. Pressing it again it will show the play symbol and still nothing happens. The player has to be switched off to stop playback.
The text how to unlock the LOCKED MODE is not localized (in German firmware the text is still in English).
Furthermore it would be nice to delete a file or folder. Right now this is only possible with the currently played file.
Thanks in advance
ps. the forum spellcheck is funny. It wants to replace SansaZip with Assassin