my bad, it was my files that had a problem. So (1) isn't a problem with the dap. But the volume spike phenomena still occurs unfortunately. And there's yet another bug:
Pressing the forward button (physical button) does not skip the song properly through the list of songs. Eg while playing song A, when I press the forward button, it plays Song A from the start again, sometimes it plays Song B, and when I press the forward button, it plays Song A instead of Song C, and if I have say 10 songs, I will only be able to play maybe 3 songs out of the 10, that is, the forward button will randomly either play back the same song again or play a new song but only amongst the 3 songs. (eg a sequence could be, Song A, Song A, Song B, Song C, Song A, Song B, Song B etc)
However the software forward button (ie. pressing the forward button on the touch screen itself works perfectly. I can forward to the next song correctly, and all 10 songs are played in sequence.
Anyone has these bugs?