union member sort function not entirely working

Hi there, and I apologize if this is a known issue, but I didn't encounter it in my searching.

I am an officer in a union, and my fellow officers and I have been trying to invite other GS users we think would be interested in joining. So as not to duplicate our invitations and annoy the invitees, I wanted to sort in the member admin tab to see if a particular user has previously been invited. Problem is, after the site thinks a minute, it only gives me the list of current members. So apparently the invited member sort doesn't work. New member sort works just fine, however. Here's a link for admins to use to look at our union member screen. I thought GS would want to know in case this is widespread. Obviously, it's not a huge problem, just a minor thing. Thanks!