The property item_number must be common to all sources or the property item_number has inappropriate data type

Solution: With poly items, each property called out in the poly item must exist in all of the item types added to it and have the same type in all of the item types

Ex: If you are adding Part, Manufacturer Part and Manufacturer as Poly Sources for Poly item.
Then you should delete Item_number, manufacturer_id and Name from properties under Poly Item.
Mean you should add properties which are common to all Poly Items