Hi MickLead,
Thanks for reaching out here in the Apple Support Communities. We see that you're having an issue with adding contacts on your Mac, and we're glad to take a look with you.
Let's first take a look to see if which type of account you are using to add the contacts, since different internet accounts can all have different Contacts account.
For example, if this is happening while trying to add someone while using one Contacts account, try switching to a different account, and see if the issue still happens.
This explains about the different accounts:
Add contacts from iCloud, Google, and more to Contacts on Mac - Apple Support
Let us know what happens.
Take Care.