Steps to reproduce the problem:
As soon as the trianer's voice starts, the audio playback in Google Play Music is paused.
I am using a Samsung Galaxy Nexus with Android 4.2.2 and Google Play Music version 5.1052J.707098.
I have had the same problem but it just pauses the music. A quick press of play fixes it
With the latest update, this problem is now gone. Works great on my Galaxy Nexus with Google Play Music.
Thank you, Skimble.com Development Team!