I have the same issue and it may be related to the post above by @dumahim. You see, I listen with Poweramp in my car (when not using Android Auto) and have about 5000 songs on my device that I shuffle through. However, the steering wheel control for playing the next track is kind of glitchy and will sometimes trigger the following after a single, deliberate press:
Go to the previous track.
Go to the previous track, then play the next track (a.k.a. repeat the current song. I know it's registering 2 clicks because the "beep-beep" sound between forced song changes plays twice in rapid succession)
Go to the previous track, then play the next track, then hold the button, causing fast-forward to occur.
I have a feeling it is messing up the list counting and causing songs to repeat, or something. I'll have to run more tests by listening while not driving or simply not using the steering wheel controls to change song.