PostgreSQL Streaming Replication - LOG: archive command failed with exit code 1
There are two possibilities:


You have archive_mode = always on the standby.

Then the standby server will try to archive WAL segments (redundantly).
The standby server is not really a standby server, but a standalone database. That means that you have made a mistake setting up the standby server.

The way to determine is that is the case, run

SELECT pg_is_in_recovery();


If that returns FALSE, the server is not a standby.