Weird problem noticed today...

This has never happened before but in my Bluesound Node 2i today there is - I can it descrbe is as - bass slap or pop, I think just coming from the left Maggie. I pretty much only play loud. My subs are right behind the Maggie (16" or so) and it's definitely coming from the Maggie. Now the DAC on the Bluesound has a lot more boomy bass than the CD player DAC - Yamaha Aventage BD-A1060. So I am thinks my it's signal-related but perhaps it's the Maggies only they are not being driven hard in those frequencies enough to make that horrible sound. BluOs just did an update that is only major change to system today. I probably hadn't played music on a couple weeks and BluOs asked me to do update then I noticed problem - could be coincidental though could this be an amp or preamp issue?
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.

Yes BluOS tone control is off. Been procrastinating as I am afraid of result (though they are still under warranty). First I will swap left to right and see.

Weird I can't seem to hear it on CD. 
So the ribbon "slapping" isn't fatal? I was not playing it any louder than I ever do. 
What model of Magnepans do you have?

You might want to do a reboot/reset on the Node2i, just to make sure it didn't get "stuck" when updated.  I just updated mine and didn't notice any anomalies.