You are getting the error message 'Please Use Not More Than 1 Party(ies) Of Role XXX' (where XXX is a Party Role).
Reproducing the Issue
Go to Sales Work center.
Go to Sales Order view.
You get the error'Please Use Not More Than 1 Party(ies) Of Role XXX'.
This error message is triggered when the Party Role XXX is defined as unique in Business Configuration.
Unique Party role can only exist ones in the document. If the Party Role XXX is exceeding one entry, an error message shows up, but still the system allows to save the inconsistent transaction.
In order to remove the error message you either maintain only one entry for Party Role XXX under Involved Parties OR follow the below mentioned steps:
Go to Business Configuration work center.
Go to Implementation Projects view.
Click on Open Activity Lists.
Search for Activity 'Sales Orders' and open it.
Click on 'Maintain Involved Parties' hyperlink.
For Party Role XXX uncheck the Unique checkbox.
Save the changes.
Sales order , party role , unique , KBA , involved parties , LOD-LE-CQP-CO , Lean Sales Orders , Problem