In view of the information gathered during this investigation, no determination as to the cause of the incident seat structural failure has been established. With over two million subject and Britax peer child seats in service, no additional structural failures were identified. Given these circumstances, ODI is closing this investigation. Closing PE21-007 does not constitute a finding by NHTSA that a safety related defect does not exist, and the agency reserves the right to take additional action if warranted by future circumstances.Please see attached closing document for a complete summary.