Another update:

Sherwood finally responded to my customer support email and told me they highly doubt it's a hardware issue. They want me to test by calibrating off-centered. However, if that doesn't work, I'm not sure what my options are. I've thrown together some rough DIY Broadband Bass Trap plans, but I wish there was a better way to pinpoint the problem. I'll probably end up doing the panels regardless of the issue because it'll give me a nice after-work hobby .

Jonathan, I'm not sure if you're still monitoring this thread, but I was hoping you could give me your opinion on my DIY project. Basically I plan on making four 24" x 48" x 5.5" frames out of white pine. I plan on filling them with 4" of 1280 Mineral Wool, giving them an extra 1.5" of air (which I read improves efficiency). Will spacing those across my back wall do the trick (or at least a trick?) Thanks.