Debugging problems with Contact Object Sync - Contact ID replaced with GUID
Sometimes when using Marketing Cloud Connect, synchronizing Contact Object from Salesforce to Marketing Cloud can generate contact key as a GUID instead of the 18 digit ID and has an 'Unspecified' as source.
Issues with GUID
Contacts in Sales Cloud have an ID (primary key) that can be used to identify that contact record. When these contacts are synchronized to Salesforce Marketing Cloud, the contact key is supposed to be the ID of the Contact record which acts as a Subscriber Key to maintain a seamless flow between Salesforce and Marketing Cloud.
In scenarios when deleting the contacts while the data sync is still in progress, the deleted contacts lose their ID in the synchronized data extension and get a GUID (hyphenated alpha numeric characters) instead. This causes downstream logic to fail as Sales Cloud cannot identify that subscriber with GUID as the contact key.
How to fix the issue?
Make sure that the Contact Delete is enabled under Marketing Cloud Contact Builder - Contacts Configuration.
Under manage settings, the suppression period for Contact Delete by default is 14 days which can be modified as per the need.
Pause the data synchronization process for the Contact Object. Create a sendable data extension to extract all the contact keys from synchronized Contact Object Data Extension using a SQL query activity.
Under Contact Builder, All Contacts - Click on Delete contacts from data extension
Select the sendable data extension in which the query data is loaded and check the Delete both contacts and data extension to delete the contacts.
Deleting the contacts from this data extension removes associated information and relationships across all provisioned channels along and also deletes this Data Extension.
This action cannot be undone.
The status of the contact deletion process can be monitored in the Contacts Analytics dashboard.
Resume the Contact Object data synchronization.