having problems us ng my ipod 7g Nike Fitness. When running when I press the button between the volume buttons, I get a different action almost every time.

I am having problems using my ipod 7g with Nike Fitness. When running when I press the button between the volume buttons, I get a different action almost every time. And usually I end up either turrning volume up very high or ending the workout. I need to be able to pause workout, and get spoken feedback regarding time, distance, and pace, that's all. I'm using a Griffin brand armband, that covers all of the buttons. I've read the online manual. no help. I'm just about ready to return it and go back to my 5th gen with its smaller song capacity and no blurry. Any help or suggestions very welcome.