Replication conflicts despite hot_standby_feedback = on?

[Laurenz Albe <laurenz.albe@xxxxxxxxxxx>]

I'm seeing the following at a customer site:

SELECT confl_tablespace, confl_lock, confl_snapshot, confl_bufferpin, confl_deadlock
FROM pg_stat_database_conflicts
WHERE datname = 'something' \gx

-[ RECORD 1 ]----+------
confl_tablespace | 0
confl_lock       | 0
confl_snapshot   | 84990
confl_bufferpin  | 0
confl_deadlock   | 0

SHOW hot_standby_feedback;

 hot_standby_feedback 
----------------------
 on
(1 row)

This is PostgreSQL 11.7, the standby didn't disconnect from the primary, and
the number of replication conflicts is growing.

I had thought that "hot_standby_feedback = on" would get rid of such
conflicts.

In the code I see a lot of call sites for ResolveRecoveryConflictWithSnapshot,
so it is hard for me to track this down.  Does anybody know what could cause
these replication conflicts?

Yours,
Laurenz Albe