Scroll down to the second divider (it says "bar" at the top).
Note the names above and below the divider. Then click the button to add a new name to the first group. You'll see the new name at the bottom of group 1, but the top of group 2 now has a new first name (whatever was previously the 2nd name in group 2). The first name in group 2 has disappeared.
You can view the issue here: http://jsbin.com/cedira/4/edit?html,output
Scroll down to the second divider (it says "bar" at the top).
Note the names above and below the divider. Then click the button to add a new name to the first group. You'll see the new name at the bottom of group 1, but the top of group 2 now has a new first name (whatever was previously the 2nd name in group 2). The first name in group 2 has disappeared.