You must have a problem with the NFS mount itself, that's where your problem is. I would check the NFS server logs, because that's where the problem should be.
But that is not the problem.
The datastore is mounted correctly and a while after it has mounted the name is changed by ESXi.
The DS is only mounted and unmounted by that two servers by script and as it is the same physical DS there should be no problem if the name is the same on both ESXi servers.
So you must have this same datastore mounted elsewhere, that's the only reason you see the (1). VMWare uses the unique name not the human readable form to connect. That name you give it is just for show, it's a label.
But for us it is a problm cause we use that name in vmkfs cloning operation.
Thanks for your thoughts.
Cheers.