Trying to add a line to a Procurement contract and getting illogical error.

We have an active contract that has had releases against it.  User wants to add a new line to contract.  Receives error message shown in attachment saying "Contract line is being processed. Cannot change line."  Looking at record CNTRCT_RLS_HDR for contract, all rows show release status of C (complete).  Why can't another new line be added to contract?  We are on release 9.0.  Where can I look to see if there is really something in process?

Looking at the People Code, it seems to be firing that error when the release status on CNTRCT_RLS_HDR for contract is not equal to O(open).  Why would Complete not be allowed? Is this a bug that was fixed in a later version?