I was a Magnepan dealer for many years. Without really seeing/hearing the problem, my best guess is that you’re simply over-driving the panel.
This is known as "panel slap". Especially in the bass region. The panel can only move so far. If it’s over driven it will cause this to happen.
You will really need to isolate the problem. Could be with the electronics. Troubleshooting it all the way through is best. Isolate each piece and follow the clues...
Also, the BluOS has a tone control setting. Make sure it is "off" or that the level is at zero. Could be you're pushing extra bass, (or treble) through the Node 2i.
This is known as "panel slap". Especially in the bass region. The panel can only move so far. If it’s over driven it will cause this to happen.
You will really need to isolate the problem. Could be with the electronics. Troubleshooting it all the way through is best. Isolate each piece and follow the clues...
Also, the BluOS has a tone control setting. Make sure it is "off" or that the level is at zero. Could be you're pushing extra bass, (or treble) through the Node 2i.