See Guidance ISO/TR 14969:2004 explanation or clarification for section 8.5.2 and 8.5.3.
If product related issues, you could look at other sources of quality data, e.g. complaints, service calls, field returns, replacement part shipments, besides the usual nonconforming material records.
If supplier caused product related issues, above mentioned data sources usually are the first ones to be looked at.
Depends on the degree of the problems, you could also look up engineering change requests and number of subsequent ECOs on same or similar issues. For example, if the issue originally is a specific component in a subassembly, you could also run a NCR, ECR, complaint, service calls data (for examples) to see if anyone has complained or raised issues about the subassembly that may be caused by the component.
If the issue is process related, you could add a re-audit to the internal audit schedule for that particular process. You could wait a couple months and then pull some samples of the records to evaluate if the fixes were indeed effective.