The people that posted pics with the figures inside a glass display case have you encountered this annoying rattle because of the glass floor for a particular level is not sitting flush with the rest of the corners. If you were to lay a glass panel on a level you look at each of the four corners that makes contact with the clear rubber plastic mounts I have one corner that's not resting on that clear plastic mount there's a gap I can push my finger down on that corner it would tilt down and pop back up when I let go. It's annoying when I walk near by the case you can hear it rattle/vibrate.
I might have to just stuff something in there to make the gap go away but hopefully it won't stick out like a sore thumb.
I have that problem with one of my detolf shelves where one corner isn't in contact with the bar. I placed some clear Rubber Cement (or you can use clear Shoe Goo) on the corner to build up the contact and let it dry. Works great, now I have 4 point contact and its mostly invisible too!