You can get the source from githib datastax/java-driver. It doesn't look like the source is included in either the maven or tarball downloads.
I think you are encountering CASSANDRA-6722 when you used IN and ORDER BY in your query. The java-driver automatically does paging with a default fetch size of 5000. You can disable automatic paging with Statement.setFetchSize(Integer.MAX_VALUE)
. There is more info about automatic paging in this blog post.
What version of Cassandra is you application connecting to? If you could share more about your table definition and query maybe it will be possible to reproduce the repeating rows issue.