Foreign key violations detected upon UPDATE on another column

I have a table country that is referenced by many tables like so:

db=# d client
                          Table "public.client"
      Column              |            Type             | Modifiers 
--------------------------+-----------------------------+-----------
 id                       | character varying(32)       | not null
 name                     | character varying(64)       | 
 country_id               | character varying(32)       | not null
 insert_date              | timestamp without time zone | 
 update_date              | timestamp without time zone | 
Foreign-key constraints:
   "client_country_fk" FOREIGN KEY (country_id) REFERENCES country(id)
Triggers:
    update_client_insert_date BEFORE INSERT ON client FOR EACH ROW EXECUTE PROCEDURE update_insert_column()
    update_client_update_date BEFORE UPDATE ON client FOR EACH ROW EXECUTE PROCEDURE update_update_column()

The referenced table:

db=# d country
                              Table "public.country"
       Column             |              Type           |  Modifiers   
--------------------------+-----------------------------+--------------
 id                       | character varying(32)       | not null
 name                     | character varying(256)      | 
 insert_date              | timestamp without time zone | 
 update_date              | timestamp without time zone | 
 Indexes:
"country_pkey" PRIMARY KEY, btree (id)
Referenced by:
    TABLE "client" CONSTRAINT "client_country_fk" FOREIGN KEY (country_id) REFERENCES country(id)
Triggers:
    update_client_insert_date BEFORE INSERT ON client FOR EACH ROW EXECUTE PROCEDURE update_insert_column()
    update_client_update_date BEFORE UPDATE ON client FOR EACH ROW EXECUTE PROCEDURE update_update_column()

And the trigger :

db=# SELECT proname, prosrc FROM pg_proc WHERE proname='update_update_column';
        proname         |                                  prosrc                                  
------------------------+--------------------------------------------------------------------------
 update_update_column |     BEGIN       NEW.update_date = now() ;       RETURN NEW ;    END ; 

I discovered by chance that these foreign keys were violated when running an UPDATE command on one of the tables:

UPDATE client SET name = 'foo';

ERROR: insert or update on table “client” violates foreign key constraint “client_country_fk”
DETAIL: Key (country_id)=(someRandomId) is not present in table “country”.

I deleted all rows referencing someRandomId and I was able to run the UPDATE command.

How can my database be in an inconsistent state?

Can I run all database constraints manually to make sure it is now consistent?

I suspect the issue has to do something with the DEFERRABLE setting. But according to the doc, it’s not the default.

According to the doc, there’s a SET CONSTRAINTS; setting but it only applies to a specific transaction.