The Zone class contructors throw an exception if you pass in a list of records that contains both a SOA and an RRSig for that SOA.

It appears as though the underlying Zone.addRecord() method is supposed to decorate the SOA record with its associated RRSig info. But, due to this bug, it tries to replace the SOA record with the RRSig record (which fails).

See the attached stack trace: stacktrace.txt

This seems to have been introduced with version "3.6.0".