Workflow issue on service receipting

We currently have PO's on the system where the first line of the PO is matched to a cost centre, and line 2 to a project. Very occasionally when someone creates a service entry sheet on the 2nd line, if they do not do it correctly and it stays on the red traffic light, it throws up an error. Instead of the person receiving notification or up to their manager as we would expect, it automatically routes up to the person at the top of the organization. Any ideas why?