I know this thread is a bit dated but, it was only a few days ago that I experienced the buzz/rattle on my L2m.
I was using it on a stand as a monitor for a conga player, every time he hit his low conga the speaker would buzz.
long story short, I found that it was the speaker grill causing the problem. I use a piece of gaffer tape about 1 1/2 foot long around the grill from left to right, across the logo. That removed the buzz. I will soon check all screws to see if that's the real problem