Ship-to Location LOV is displaying the other customer values and not defaulting the correct value

Ship-to Location LOV at Contract Parties tab, is displaying the other customer value and no default value in LOV is coming up once the customer Account number has been selected while creating a Project based contract.

Business Scenario:

While creating a Project based Contract that is Sell Contract, on Parties tab once the "Bill to Account number" is selected it shows the Default value of "Bill to Site "column but not for "Ship to Account Number". it expects us to search on LOV and then select. Also, in LOV it shows "Ship to Account number" of other customers as well.