Need help fixing my NWZ-S639F

[katem]

My Sony mp3 player (NWZ S639F 16gb, serial number 5113526)
got squashed at the bottom of my bag and since then it has been malfunctioning. It will appear to play a song but no sound will come out no matter what the volume setting is, and the headphones are not faulty. Then it refuses to move on to the next song and if you try to navigate elsewhere it either reverts back to the first song or switches itself off and on again.


I've reset it, reformatted it, uploaded music again but the same problem reoccurs - this time getting stuck on a different song, so it's not a corrupt mp3 file. I've made sure it has the most up to date firmware (version 1.11). What should I try next?