BOM not showing right part numbers

Since we started using SW2016, I've run into a BOM glitch I haven't seen before, or at least not as prevalently.  If I create a BOM on a drawing, part names frequently come in wrong unless the assembly has been set to resolved.  The parts that come in wrong are parts that have been renamed at some point.  For example, we may have used Part A in Assembly 1.  In Assembly 2, we decided to use a modified version of Part A, and create a copy of the file and call it Part B.  When I create a BOM for Assembly 2, Part B will show up as Part A if Assembly 2 is in the lightweight condition upon the creation of the BOM.  In case it matters, the BOM field that shows the part number is linked to the file name through a custom properties field.  The value in the custom property field is \$PRP:"SW-File Name".  Does anyone know what's going on here?

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