Feb 23, 2017.
Had the issue. I bought a HumX, and it solved the issue.
My Mac is on another outlet, Plugged it into same outlet as Helix. Did NOT work.
Tried the HumX on the Mac outlet, Did NOT work.
Plugged the HumX on the Helix outlet. Mac on separate outlet. FIXED. It's definitely created by the Helix.
Line6 needs to address that USB, it needs some kind of update. Nothing to do with your Mac or PC.