Automatic reverse synchronization
From Planfix
When integration with Google Contacts is enabled, two-way synchronization occurs by default for contacts in the Planfix contact filter and the Google account. You can disable reverse synchronization from Google Contacts to Planfix. To do this, disable the setting Automatic reverse synchronization:
This should be done if your company uses Planfix as its main contact database, not Google Contacts. In this case, Planfix should not be automatically updated when Google Contacts is.