Some of the elements that are references should be refined. BreastAbnormality.part of should be MedicationStatement and Procedure, not obf-MedicationStatement and obf-Procedure (I'll show you how to use the "No profile" flag). Also, you should limit BreastAbnormality.subject to Patient and BreastAbnormality.performer to Practitioner. (Group, Location, etc. don't make sense in this context).