For CardDAV logs, in Terminal type:

defaults write -g ABMigrationLogEnabled -bool YES
defaults write EnableDebug -bool YES
defaults write LogConnectionDetails -bool YES

Then relaunch Contacts and see if you can reproduce the problem.

If so, then attach the following: ~/Library/Containers/

Then disable the logging by typing in Terminal again:

defaults delete -g ABMigrationLogEnabled
defaults delete EnableDebug
defaults delete LogConnectionDetails