Let's suppose that the tracks on your playlists have specific start and stop times. With your "old" iOS9 devices, the Music App allows you to play your music in shuffle mode without any problem. But your new iOS10, jet black, iPhone 7, bla, bla, bla, surprisingly randomly changes the start/stop times when playing music in shuffle mode (and only in shuffle mode). The interesting thing is that it seems the music player app applies the start/stop time of the first song in the (ordered) iTunes playlist to the first song (randomly) selected in shuffle mode; the same for the second song, and so on.
I think that the issue is well defined, and the solution is easy... even for the Apple engineers.
