Have you changed headphones?
Yesterday I had to use my phone for music at work as I had forgotten to charge my Walkman, it wasn't a good experience, I would play an album and after X amount of tracks it would stop, and this kept on happening all day, I gave up in the end and went music less.
I should explain some details.
I ride a motorbike all day, I use a product called Scala solo which is a Bluetooth headset for use inside crash helmets, the Bluetooth part is linked to my work phone, I normally plug a Sony Walkman into the jack input and if a call comes in it cuts the music, when the call is ended the music comes back on, I have no problems with pausing/stopping at all.
My phone is a 1520 and it works fine with normal headphones, will work all day and I have no problems.
But there is obviously something going on inside the headset that causes the phone to stop or pause the music on the phone so some kind of compatibility issues in my case.
So can you try a different set of headphones and see if you still have problems?
Bob