Yeah, Magni seems pretty picky about how it's plugged in.
At the Charlotte meet today mine decided it didn't want to work right with everything else that was in the room. For some reason the right channel had almost no low frequencies, it was pretty bizarre. However, as soon as everyone else on the circuit had unplugged their stuff it went back to sounding excellent.
In normal conditions it isn't an issue for me, but it was certainly weird today.