When there are two or more instances of the document and media display portlet in the same page, the collapsible elements of them don't work well. It seems that they have the same id's elements, and it breaks the usual behaviour of collapsing/expanding.
Steps to reproduce:
Create AFolder on root folder
Create A1Folder on AFolder
Create documentA A1d on AFolder
Create BFolder on root folder
Create B1Folder on BFolder
Create documentB B1d on BFolder
Create a new page called "displays" or another name
Add a "document ands media display portlet" to the page
Configure the viewer to see AFolder
Add another "documents and media display portlet" to the same page
Configure the second viewer to see BFolder
Enter in AFolder and return back.
At this point, the collapsables divs of "documents" and "folders" doesn't work.