Marketo records are failing to delete.
For Marketo records that are synced with Salesforce, if the Delete from CRM is True in the delete process, and the deletion fails in SFDC, then the Marketo record will fail to delete because the entire requested action cannot be completed. (action = delete in Marketo and delete in SFDC)
Looking in the Marketo Lead Activity Log will give you a more specific reason as to why the record is failing to delete.
Who This Solution Applies To
Clients integrated with Salesforce.