I experience the exact same issues with many of the CW Programs I watch. During almost all of the action sequences with loud sound, explosions, gun fire, etc, the sound "pops" in and out. It is extremely frustrating and annoying, almost to the point that I am going to stop watching CW.
It occurs on all of my TVs. One is a Verizon set-top box, and the other two are on TiVo boxes. It doesn't matter if I watch the show live or on DVR, or if I have the sound through the TV, soundbar, or surround sound. All of them are connected with HDMI, fiber optic, or digital cable.
I am reaching out to the local CW Balitmore station, too, to see if they have any idea.