While creating sales order for the product which is onhold, if the site and warehouse is not mentioned in header, then the sales order line populates the item name and other fields before displaying error. But if the site and warehouse is mentioned in the header, the item name is not displaying. Soon after inputting the item name, the error message displays. i.e validation executes before the look up field populates as all the mandatory fields are filled and data got saved automatically.

Though the impact is low, would be better to have the lookup field populates before the validation triggers