Any type of priority scanning going on or perhaps Weather or Close Call? If the "cutting out" happens at regular intervals (every X seconds) that would be my guess.
Also if you are listening to the ARMER radio system, its possible the mobile user may see it gets a better signal from an adjacent site and then jumps over to it. Scanners don't deal too well with this situation. For example the conversation is near the Cottonwood/Murray line. It starts out on Cottonwood, which your scanner is monitoring. The user's radio starts dropping off on Cottonwood and sees a better signal from Murray tower, so it jumps to that, all the while your scanner remains on Cottonwood.