I've noticed (hardly couldn't miss it) the problem on my SP too. Allthough it happened more frequently then you've reported.
I have triend every single firmware version and different music players, but nothing seemed to solve the problem.
I haven't tried it with a different SD card. Do you play your music from SD card and did you try different SD cards?
I'm using a 64GB Sandisk ultra SD, but unless that is faulty I cant see why that should be the problem. Also my phone doesn't skip music or songs so that eliminates the possibility of a broken SD card for me I guess.
At the moment my phone is in for repair, dead pixels on the camera image sensor, but I told them to have a look at the music problem too.
Any thoughts on how this problem could occur?