[App_rpt-users] Audio ' Clicking '

At ETSNJ, we run 2 repeaters off a Raspberry Pi. After a few days, the audio begins to suffer brief interruptions with a clicking type sound. It progressively gets worse until it is chopping up the actual conversation. I can clear it by re-booting the Pi, but it returns after a time. I've looked at the running processes, and do not see anything abnormal that would chew up processor resources. Anyone have thoughts on what this might be?