Although for me it's on GS4 and I'm not using any fx in GS. I've tried building a new performance and recopying the samples, so far I can't get it to go way. I'm running XP64. I loaded the same samples into kontakt on this machine and using the same hardware (RME9652) the artifact is gone. Additionally, I played the samples in question on my mac in GPlayer with no artifacts. If I didn't have a large chunk of giga files I would ditch GS4 altogether but for the moment I need. I would be curious if anyone has had similar experiences.