One thing I noticed on my Rezound, if I opened up another application while listening to my MP3s, if I try to use the Bluetooth controls, the application that I last launched will interfere with the controls. Thus, try disabling all non-essential apps running in the background prior to launching your MP3 player to see if that helps.
Only problem with that is if you were last using some other application and let the phone sleep and lock for a while and then grabbed your headphones to initiate a call or music, you would have to manually unlock your phone to close those apps OR try to remember to close the non-essentials before you let your phone go to sleep and lock; either way, that would still remove some of the convenience of Bluetooth.
Posted via Android Central App