Clicks and pops with more than 4 voices

I cannot create a schedule with more than 4 isochronic or binaural voices without getting a lot of clicks and pops. These clicks and pops are present when export to audio file and play with vlc. I have the latest Gnaural 1.0.20110606 and am using windows XP.

To experiment with this problem, I created a schedule with 5 voices ALL binaural with a beat of 4 and base of 180. At first there was a buzzing noise. After muting one voice and unmuting it the buzzing went away I played the schedule a couple of times and it was fine. Then I changed one voice from a beat of 4 to 8. Then there was an annoying buzzing sound. I muted and unmuted the voice and discovered that much of the time I muted and unmuted it had a lasting effect on the sound. I could make the buzzing go away or switch it from both speaker to either one of the speakers just by muting and unmuting one voice repeatedly. The effect on the buzzing lasts through repeated plays. I got the buzzing over to my left speaker and then shut down the program and reopened. When I loaded and played the file the buzzing was now in both speakers but I can still turn the buzzing off and move from from one speaker to the other or both by repeatedly muting and unmuting.