[Evolution] Contacts/Address book error: Move a contact list from one address book to the other

["theapplepie differentmail com" <theapplepie differentmail com>]

Hello!

Ubuntu 20.04 LTS, Evolution 3.36.5-0ubuntu1

I have two local address books (under "On This Computer"). I would like
to move a contact list from address book A to address book B. But I
always get following error:

Error adding contact
Cannot add contact: Conflicting UIDs found in added contacts

Trying to copy the contact list gives the same error. I saved the
contact list as vcf-file and tried to import it into the other address
book - nothing would happen but I did not get an error, either.
A newly created contact list can be easily moved without error.
Did I make a mistake in the past?
I tried to find a solution online but what was not successful.
Can anyone help?

Thanks

Dan