Requisition got posted and unposted automatically when Automatically Unpost Requisition is set to No

Summary:

Requisition got posted and unposted automatically when Automatically Unpost Requisition is set to "No" 

In the Progress history we can see the req was posted and Unposted with only date when it is done and there is no fast formula is set to post or unpost the reqs. Please suggest if is there any query/table where we can check who performed the action or how the action was performed.

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