Some songs can't be played using Music app on iOS
The stop sign shows that the file can't be played. This is usually due to a corrupt song. When the music app attempts to play one of these corrupt songs, it fails and skips to the next song. This is why you can't go back a song, since when you go back it attempts to play the song, fails, and goes forward (back to the song you started at).

Make sure that the songs play in iTunes, then delete the songs from your device and re-sync them from your iTunes library, making sure that the sync is complete before disconnecting the device.