It basically means that there's something wrong.
Please provide more details about your environment, and the backup configuration. Without any details it's hard to tell what may be causing this.
We have a server running veeam 9.5 used to backup the vcenter 6.5 guests server to a hitachi san device using NFS and located in a remote building from the vmware setup. At 7:am in the morning, when backup are running and at noon when they are not running three of the esxi server in one of our clusters is showing that the backup server has lost connection and is in a all paths down state briefly and then its back to normal
I still cannot find a reason that I would have a all paths down going to a Veeam backup server, any ideas? I thought that would be an issue trying to connect to SAN or NAS storage not a backup server