Voicelive 3 Extreme - vocal crackling


My wife and I are career working musicians. I bought her a VLX3 for Christmas and there is intermittent bad crackling when she kicks on the harmonizer. Have dialed the gain back from 25 to 15 and still happening. I think we turned on the clip killer but it isn't clipping. She's using a Super 55 and the dynamic mic setting. Any advice?