I found that after upgrading my phone to Android 4.2.2 that headset button presses were sometimes not being recognized by JP. I’ve added code to better follow the most recent Android SDK rules for handling audio focus—that is, making sure to interact properly with other audio apps. I believe this has helped. If the headset buttons aren’t being recognized by JP, just go into the app and stop and restart play. This will allow JP to acquire audio focus and also start recognizing headset button presses.
And thanks to a person using JP by the name of Joe, I found out M4A audio files are supported by Android, so they can now be added to playlists.
Finally, I’ve had a couple reports from Samsung Galaxy S III users that JP will randomly hang up during track changes. Working with my trusty friend and beta tester Dan, we concluded that it has something to do with the gapless playback code I added a while back. So, if you have this problem, you can now disable gapless playback in the Preferences and it should go away. It’s a workaround and not a fix, but I can’t duplicate and isolate it on my Galaxy Nexus, so this’ll have to do for now.