Problems signing .rpm which was built with rpm v3.0.6

Issue

When an attempt to re-sign an RPM package built using RPM version 3 using RPM version 4, the re-sign fails and I see the following types of warnings within package information:

# rpm -qip <package>.rpm
warning: <package>.rpm: Header V3 DSA signature: NOKEY, key ID <key_id>
<etc>

Occasionally this can also corrupt the resultant package.