First figure out which database is having that issue, by using pg_dump --schema-only on each database in turn. Then run this SQL on the database giving the error to see if the type exists, or what is nearby:
select oid, typname, typtype, typnamespace::regnamespace from pg_type where oid <= 794978 order by 1 desc limit 3;
Also let us know the version of pg_dump and the version of Postgres being dumped.
