DKIM failures with Yahoo, despite passing SPF and DMARC, can arise from various technical issues. These include invalid DKIM signatures due to email content modifications during transit, domain mismatches between the signing domain and the 'From' header, syntactically incorrect signatures, unavailable public keys, failed signature verification, incorrect key deployment, DNS propagation issues, and mismatches between the DKIM selector and the configured DNS settings. Proper troubleshooting involves examining email headers, DNS records, and mail server logs to identify the specific cause.