Contact Data is Completely Scrambled

I am using the most recent version of software and suddenly my contacts are completely scrambled. I noticed a few weeks ago that a couple of email names were wrong. The summary column on the left showed one name, but when I opened the email, it was from a completely different person. I checked my contacts and that is where the problem lies.

The names that have gotten scrambled have nothing in common (e.g., one name DN got combined with one with the initials JH). I also now have a bunch of people in there that I never added and have no idea who they are. It is mostly emails, but I don't know if the phone numbers for these people are actually their numbers on numbers that belong to some legitimate contact that I need and were incorrectly merged with these contacts, so I can't delete them.

I found an old thread on this, but the address book is not in the directory suggested, so I can't try that solution. I don't know when the problem started, so don't even know if I have back ups that old.

I do not have any social media accounts, nor did I accidentally hit 3 keys at once (even if I did, the names that got merged should not have been).

Does anyone have a proposed solution to this mess?