The direct answer
Use one qualifying BIMI assertion at a selector name. The current protocol draft stops discovery when multiple assertions remain. Several strings inside one TXT record are a different case.
Why can a DNS result show several quoted strings?
A TXT record can contain multiple character strings that are joined to form its value. A DNS tool displaying those strings separately does not necessarily mean there are multiple BIMI records. Check record boundaries before deleting anything.
Two independent records each beginning with v=BIMI1; at the same name are different: the receiver cannot treat them as an ordered preference list. Revision 15 of the BIMI Internet-Draft, a work in progress, describes the discovery rule.
How do I resolve an actual duplicate?
Compare the records with the approved logo and certificate configuration. Identify which value is intended, preserve the previous values in the change note and have the DNS owner remove the competing assertion.
Query the final public name after the change and re-run validation. If the intention was to use different logos for different streams, review selector support instead of placing alternatives at one selector.
Sources & further reading
Provider guidance checked on . Requirements can change; check the original guidance when implementing. Planning checklists and examples are BIMI World’s editorial suggestions.