Volume drops low, returns within a few seconds - Intermittent problem

I just had Directv installed and I am experiencing an intermittent drop in the volume. There does not seem to be any pattern as to when it happens, nor can I pin it down to any station.  The volume drops down low, then returns to normal within a few seconds.  I have the Choice Package with a R16-500 receiver.  We are using the SWM feature (so that I only have 1 cable instead of 2), and we are hooked up to our TV with RCA cables (yellow, white, red).  We do not have a home theatre set up.  The audio setup on the receiver has Dolby turned off.  We had a technician come to check it, and everything with the hook up and dish is as they should be.  He also updated the software.  I know they have been several posts about volume problems, but haven't found any with the same type of setup that I have.  The technician said he has never heard any complaints about the volume and says the next step is to try and replace the receiver.  I'm not sure what I should do next and would appreciate any comments that might help.