Fixed the issue. A battery had gotten loose in shipping. Once I reinstalled it, the problem magically went away.
Here's a quote from my newly updated O2 ad:
Comparison to my M-Stage amp:
It came down to a serious toss up with the M-Stage, and basically the bottom line is this:
The O2 by far has more clarity, detail, and sonic accuracy in my opinion. It is a great amp. But the M-Stage has a bit warmer, "tube-like" sound, and since I love tubes, I'll stay with it instead. However, the M-Stage lacks a lot of the accuracy, presence, clarity and detail of the O2 so it is at great sacrifice I do it. It just boils down to my particular preference for tubes, which I currently can't afford. So the M-Stage is the one I'll keep, at least until I can afford a WA6.