These indicate a malformed master zone. You can identify the exact records involved by transferring the zone using dig then running named-checkzone on it.
dig axfr example.com @master-server > tmp named-checkzone example.com tmp
A CNAME record cannot exist with the same name as another record except for the DNSSEC records which prove its existence (NSEC).
RFC 1034, Section 3.6.2: "If a CNAME RR is present at a node, no other data should be present; this ensures that the data for a canonical name and its aliases cannot be different. This rule also insures that a cached CNAME can be used without checking with an authoritative server for other RR types."
