That lockout event is caused by SYSTEM; are the no prior 4740 events not caused by SYSTEM?
Also, has SDCADCPRD01 the PDC role or not? If not, look for 4740 on the PDC.
Alternatively, you can use a tool such as ALTools to perform the digging for you - see https://www.microsoft.com/en-us/download/details.aspx?id=18465
DevAdmin account locked out frequently

Sree
1,966
Reputation points
Account is getting locked out frequently. We are having an frequent account locked out issue with DevAdmin account. We tried to identify 4740 event ID for caller computer name please find the attachment for the ref.
this is service account. mailbox is hosted in on-premises.
attaching the PS transcript
[150461-11.txt][2] [2]: /api/attachments/150461-11.txt?platform=QnA
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Michel de Rooij 1,516 Reputation points Microsoft MVP
2022-03-07T22:51:16.787+00:00