As you already know from a previous post, I recently upgraded to OS X El Capitan. Everything has been fine so far except for Google Contacts syncing. I don't use iCloud for much anymore since I signed my life away to Google services and up until the previous Mac OS X release, Google Contacts syncing seemed to work just fine.
Then something happened in El Capitan. Not sure if it's on Google's end or on Apple's end, but something changed and now whenever I make changes to a contact or add a contact, the Contacts app goes unresponsive for a good minute or so (sometimes crashing altogether).
HERE'S HOW TO FIX IT
Go to System Preferences > Internet Accounts
Uncheck "Contacts" for the Google account
Click the "+" to add a new account
Set Account Type to "Manual"
User Name is FULL Gmail address
Password is password, or a new app-specific password if 2-factor authorization is "ON" for Google
Server Address is "google.com"
And that's all! Now your Contacts on Mac OS X El Capitan are as responsive as ever!