ERR - Cannot write to STDOUT. Errno = 110: Connection timed out

First - you may be expecting a bit given 6.5.4 has been out of support for some time, and 8.1.2 doesn't officially support anything below version 7.6.

A couple of questions.

1. How large is the file system causing the issue?
2. Does the client have IPv6 enabled?

For 1. If the answer is large - then review this article and see if it applies   https://www.veritas.com/support/en_US/article.100003560

For 2. If the client has IPv6 enabled, review this article (basically disable IPv6 if you are not using it)   https://www.veritas.com/support/en_US/article.100022013

Hi,
At a first look to the logs, your problem is here :

18:00:16.796 [16638] <4> bpbkar: INF - Processing /

Here one more than hour.. for next line ..
And then the next line is a warning regarding /archives_bck which is on NFS FS
19:02:33.157 [16638] <8> bpbkar: WRN - /archives_bck is on file system type NFS. Skipping.

AND AFTER ALMOST 12minutes..
the error comes with a timeout..

19:14:53.348 [16638] <16> bpbkar: ERR - Cannot write to STDOUT. Errno = 110: Connection timed out
19:14:53.348 [16638] <16> bpbkar: ERR - bpbkar FATAL exit status = 24: socket write failed

First we need to take a look at your policy configuration

Are you backing up some mount point?

Has this worked before?

Please put full detailled status and also take a look at bpbkar log with high verbo and bpbrp on media server side ..

Good luck