Question about Signed Repository Contracts

We imported a bunch of 11i contracts to R12.  These have to be created in "Signed" status.  This is not what our users want.  They'd like to be able to add parties (as the import process limits us to 3 parties).  I tried to use the OKC_REP_UTIL_PVT.change_contract_status API to change the status to "Draft".  This let us add parties to the contract and submit it for approval again and was flagged "approved" later.  However, now we cannot change it to "Signed" and add sign parties as it returns a unique constraint violation on columns (CONTRACT_ID, CONTRACT_VERSION_NUM, PARTY_ROLE_CODE, PARTY_ID) on table