These don't seem like normal locks. Nothing shows up in a "SELECT relation::regclass, * FROM pg_locks WHERE NOT GRANTED;"
These processes are all active but the wait_event and wait_event_type fields indicate they are waiting on (I believe) shared memory locks.
pid | usesysid | usename | application_name | state_change | wait_e
vent_type | wait_event | state
--------+----------+--------------+---------------------------------------------+-------------------------------+-------
----------+---------------------+--------
165024 | 16392 | content_user | application | nymapp01.nym | 6192 | 2018-03-07 09:19:09.770155-06 | LWLock
Named | SubtransControlLock | active