I should have explained the rules better. Only 1 unvoided preferred name is allowed for each locale. Case doesn’t matter. I should have added the voided field to the query. Your results show 2 preferred names for ‘en’ – ‘UNKNOWN’ and ‘Unknown’. Maybe one is already voided. 2 preferred names will not be validated during metadata sharing. Best to change the locale_preferred instead of changing the locale.
Try using this query to confirm voided status:
select concept_name_id,name, locale, locale_preferred
from concept_name
where concept_id = 1067
and voided = 0
order by locale;