As soon as there are 297 contacts in Fastmail, you don’t need the app anymore.
I don’t understand what you’re talking about here, as my goal is to keep all 3 contact repositories in sync:
I meant that you don’t need the “Copy Contacts” app anymore. Syncing between 3 places (one of them with DAVdroid) is a common use case. I’m syncing between Nextcloud / Evolution / DAVdroid myself.
Everything works perfectly
Happy that it now works for you. If there’s still a specific problem, just let us know.