The settings of Part ID depend on the set-up of item code in schema files. Moreover, some components in Bill of Materials are not combining even they are completely the same with one description. For instance, weld neck flanges showing in the same item number but separated. In addition, the description is the same and quantity is not giving the total number.
If above problem still persists, then please create a Service Request and contact the Bentley Product Advantage group. Please include a list of all relevant details to get in depth analysis for a solution or workaround