Four of Each Contact

Each of my contacts appears four times in the Contacts app. The problem is, when I try to delete the duplicates, it deletes all entries for that contact, as if they're somehow linked. I see the same behavior on two of my Macs (signed in with the same account), but my iOS devices only show one entry for each contact. I have gone to Contacts > Preferences > Accounts, and I only see one account enabled, so it's not an issue of multiple accounts' contacts conflicting.

The other weird thing, and I think this is the source of the issue, is that I see many different entries in "Groups," all of which are just called "card." Each of these contains mostly the same contacts.

Any advice on how to proceed? Do I just need to turn off all contacts, and then re-add my one account? Or is there some way I can delete some of these "cards" to resolve this?