I recently purchased an MPulse 600. While I am very satisfied with the sound, I am beginning to wonder about Mesa's quality assurance. The first time I went to use the effects loop, it failed. A week later I was at a gig that did live recording and the Direct Out jack kept shorting out. I've talked to a few folks that have had bad luck with the smaller Walkabout. Anyone else experiencing "issues"? How has Mesa handled them?