Some times the address that Google geocoding returns is different from the address stored on a profile. Often this occurs for rural or incomplete addresses. Currently when this happens, the state and county will be updated with the address returned from Google. This shouldn't happen for registered addresses, since those addresses come from the voter file and should not be modified.
The integrity of our customers data is very important to us, and we understand that sometimes the incredibly valuable process of geocoding addresses can cause some unwanted modification of address data. We also know that this is particularly sensitive for registered addresses so we'll be investigating.