I am trying to use Using ReqIF Studio from FormalMinds to do a difference of two ReqIF file. 

The first file went to a supplier who imported it into their DNG, made some changes and re-exported a ReqIF file.

Before I import back into my DNG - I want to do a Difference of them.  ReqIF Studio is suppose to do that. But I get a casting error.   The error is:

org.eclipse.rmf.reqif10.impl.SpecObjectTypeImpl cannot be cast to org.eclipse.rmf10.Specficiaton Type

Has anyone used ReqIF Studio or have another method of checking roundtripped Reqif files  before importing them?

Thanks, Carol