Application becomes periodically unresponsive to keywords.

So far my application is working very well and will run for several hours (and days) with no problems and excellent keyword recognition.
However, it will occasionally "stop listening" for several minutes and become unresponsive when keywords are spoken.
This is generally when the device is in a quiet room where I program.

I have also tested the device in noisy environments (with a radio playing rock and roll music) and am familiar with the five to ten second period of time after the radio is turned off, before the application starts recognizing trigger words again. The first case is different. I often have three or four devices running the application at the same time, when one will stop listening for several minutes.

Any thoughts regarding what may be causing this? Thanks in advance.