Postgresql: invalid record length at 29/E4624520 but replication looks fine
I cannot do anything else than quoting an entry from the pgsql-admin mailing list:


  Just after startup, the standby tries to read and replay the WAL files
  which exist in the standby, and then if it finds invalid WAL record,
  IOW, it can no longer read valid WAL record locally, it starts
  replication and tries to read the WAL files from the master. So the
  above log message "invalid  record ..." means that there is no valid
  WAL record in the standby, which triggers the replication. Since valid
  WAL records are streamed from the master, you don't need to worry
  about that log message.


It's worth noting that that line is only a LOG level message.