Is there any system validation done on the requester who created the work confirmation?

We have a complex SPO in which  the work confirmation has been approved and name in the invoice workbench requestor field is no longer with the company.  The system has created two system holds as identified below.

Is there some type of validation done on the requestor field which would cause the above error message?

1.  Amount Billed is greater than Amount Ordered * (1 + % Ordered
tolerance).

2.  Amount Billed is greater than Amount Received * (1 + % Received
tolerance).

Is everything on the work confirmation and the invoice workbench look accurate.  We do 3 way match.   The work confirmation is approved but on the work confirmation view screen it has approved as 0.00.  We have this same situation happen last year in which the requester name on the invoice workbench this name appears to be the employee (person who has left our company) who created the requisition and is autopopulated when the accounting clerk created the invoice on the invoice workbench.