Looks like there is/was a similar problem in MySQL.
How to reproduce in PostgreSQL:
create type y_or_n as enum ('Y','N');
create table enum_test ( id serial, answer y_or_n );
Now try to edit or add a row in the enum_test table using the data tab for that table.
It should allow Y or N in the 'answer' column, but the following error is
produced:
DBCException: SQL Error [42804]: ERROR: column "answer" is of type y_or_n but expression is of type character varying
Hint: You will need to rewrite or cast the expression.
Position: 46