Syncing Contacts via iCloud only; 3 duplicate iCloud lists of groups appear on one of my computers

Hello, I have two computers, a Macbook Pro (mid 2014, OS 10.10.3) and a Mac Pro (mid-2010, OS 10.9.5), and two iOS devices (iPhone 6 and an iPad 2). I am syncing Contacts via iCloud only (I am not syncing Contacts via iTunes on either computer).

For some reason, on my Mac Pro, when I open Contacts, there are three duplicate iCloud lists of groups. In other words, in the left-hand sidebar in Contacts, I see "iCloud" with all my groups below it, then "iCloud" again with the exact same list of groups below it, and then "iCloud" a third time, with yet again the exact same list of groups below it. I can't figure out how to get rid of these duplicate lists. These duplicate lists of groups do not occur on on iCloud (on the web), or on my Macbook Pro, or on my iPhone or iPad.

Anyone have any ideas?

Thanks.