I suppose I did misunderstand you, but you brought up GSM shielding, so I had (incorrectly) assumed that you already related the sound break to the GSM interference.

Does the problem when you turn the antenna off? How about with an iPod? Does it only happen when the speakers are wireless, or does it happen when they're docked onto the base? How far away are the speakers from the base?

If I keep the antenna on, not only do I get severe GSM chatter, but it will also cause the sound to break up/cut out when the speakers are wireless. I haven't done extensive testing with wireless, as I don't need that feature, and I certainly haven't done it much with the antenna on, since I get so much interference that I just have to turn it off. I can try it tonight to see what results I get.

If you've turned the antenna off and you still have a lot of sound issues, I'd get it fixed/replaced under warranty.

Devices can act in different ways when it detects a loss of a connection. My stereo Bluetooth headset when used with a Jabra A125s transmitter on my iPhone will cut out for seconds at a time, while the Sony transmitter handles the interference much better so the result are very short, but successive drops. From my observations of how the Evolve works for me, I wouldn't be surprised that when the base loses a connection due to interference or whatnot, it takes time for the speaker and the base to "find each other" and then to determine which channel that speaker is supposed to be. So, I wouldn't be surprised if the sound cut out for a few seconds at a time during the negotiation phase of this protocol.

But, I don't know the technical implementation of the Evolve, so everything I just said is pure conjecture. If I had the same problems, I would try the steps that I suggested to see how the various external factors are affecting the performance of the system. Or, give Griffin a call and let them step you through similar steps to determine if the unit is defective.