Contacts app hangs when online

In Catalina, while entering anything in Contacts, every few seconds the system hangs with a beach ball. When control returns, in 8 to 10 seconds, I am still in Contacts but the cursor has disappeared. I can click again to continue entry, but the cycle starts again.

It is as if the system is checking or synching to something.

If I turn off WiFi and Ethernet, the problem goes away until I reconnect.
A fix or workaround would be appreciated.