macOS Contacts: Duplicate Microsoft 365 contacts & groups

Hi,

Pulling my hair out on this one :(. I have two macOS devices (MacBook Pro, Mac mini) - both running the same version of macOS, both connecting to the same Microsoft 365 account. I am syncing (the same) Contacts to both ... one works great, no issues at all. On the other, multiple duplicated contacts, and contact "groups" (not sure what to call them). Picture attached to show this.

I have tried ...

• remove and re-add the (internet) account. No change.
• disable and re-enable Contact sync. No change.
• I checked iCloud, none of the contacts are there (as expected, they are in my Microsoft 365 account)
• I did a full contact "clean reset" on the machine, still no change

Help?!?! Any thoughts or suggestions would be greatly appreciated.

Thanks!