Referenced configurations not being found in BOM/Contains Tab

I have a bunch of screw models with multiple configurations per part file.  When I look at the BOM or the contains tab for the assemblies using these screw models, sometimes the right referenced configuration is found, but sometimes it isn't (and thus reverts to the @ configuration).  How does PDM search for the referenced configuration?  Is there something wrong with how the assemblies were built in SolidWorks that is causing this issue?

Thanks,

Sally