MP3 Player problem

[William Burlingame]

I setup a playlist long enough to get me from one stop to another for a recent trip I made. All the songs are on an SD card, so I wasn't dependent on a data signal.. I played the list using bluetooth and Amazon MP3 player. It would frequently pause and I would have to tap the arrow to continue. The audio did not revert back to the internal speakers. When it paused, I could hear a beep on the external bluetooth stand alone speaker (Braven). I kept both the phone and speaker plugged into a charger. Now that I've returned home, I've decided to run a test. I played the same playlist using the same external speaker and MP3 player. It went through the same playlist without a glitch. I'm now playing the entire library and it hasn't failed yet (5 hours). The trip was nearly all interstate. Is it possible that the problem is RF interference? If so, what's the cure? There are a lot of vehicles that are using bluetooth.