ok, good luck! These are never fun things to troubleshoot. but a few orders of operation that we have found helpful, (in situations where network speed seems to be troublesome).
Specific to Windows Servers running DFS: the usual suspects are updates, reboots, blah blah.
Also, if any of your dfs targets are ISCSI, (and attached to your DFS server)…definitely turn off the following items on the NIC of the DFS Server, (especially if it’s a broadcom adapter), heck, you might want to try these even if it’s not ISCSI.:
Flow Control
Interrupt Moderation
Large SendOffload (IPv4 and IPv6)
Receive Side Scaling
TCP/UDP CheckSum Offload (IPv4 and IPv6)
Virtual Machine Queues
you said you aren’t using DFSR, so I will assume that this isn’t a “wrong site target issue”.
All of this is just recommendations, they do not require reboots, but obviously will drop the network connection when you make changes, so…don’t do these on the server during production.
Lastly…This is NOT to say that Rhino 6 ISN"T the culprit. Just a few other items to consider.