Case is on My Home Page Twice
A typical home page has a "My Assignments" tab that lists cases you are assigned to.
If you see a case listed twice, it means you have two current assignments ("current" means there is no End Date on the assignment).
For example, if you have a Primary Assignment and a Co-counsel assignment on a case, it will be listed twice. (Hopefully your site administrators have displayed the Assignment Type column so you can see this).
What to do? You need to end one of the assignments. Hopefully your site administrators have put the Assignments history list on case profiles, like this:
In the above example, LegalServer Staff would likely click the Edit Pencil on the Co-counsel assignment and end it.