Transfer-on-commit not working on two switches

We have 21 switch stacks on campus, nearly all of them are EX4200s

For 19 of these archive on committ is working fine, for 2 it is not

I have looked at the configs carefully and even recreated them on these two switches with no luck. Below is the two relevant sections of code from the switch config and the error message in the log.

Any idea what the problem is or where to start troubleshooting?

Config from switch

archival {
   configuration {
      transfer-on-commit;
      archive-sites {
         "scp://Tech@10.121.125.118:/Volumes/PEGASUS/Techutil/Documentation/Network/Juniper/SwitchBackup" password "encrypted password";
      }
   }
}

security {
   ssh-known-hosts {
      host 10.121.125.118 {
         rsa-key

encrypte RSA-KEY
      }
   }
}

From /var/log/messages

HS019 logger: transfer-file failed to transfer /var/transfer/config/HS019_juniper.conf.gz_20150313_065127