Event ID: 5014, 5004 The DFS Replication Service is stopping communication with partner / Error 1726 (The remote procedure call failed.)

Question

I'm replicating between two servers in two sites (Server A - Server 2012 R2 STD, Server B - Server 2008 R2) over a VPN (Sonicwall Firewall).  Though the initial replication seems to be
happening it is very slow (the folder in question is less than 3GB).  I'm seeing these in the event viewer every few minutes:
The DFS Replication service is stopping communication with partner PPIFTC for replication group FTC due to an error. The service will retry the connection periodically.
Additional Information:
Error: 1726 (The remote procedure call failed.)
and then....
The DFS Replication service successfully established an inbound connection with partner PPIFTC for replication group FTC.
Here are all my troubleshooting steps (keep in mind that our VPN is going through a SonicWall <--I increased the TCP timeout to 24 hours):
-Increased TCP Timeout to 24 hours 
-Added the following values on both sending and receiving members and rebooted server
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
Value =DisableTaskOffload
Type = DWORD
Data = 1
Value =EnableTCPChimney
Type = DWORD
Data = 0
Value =EnableTCPA
Type = DWORD
Data = 0
Value =EnableRSS
Type = DWORD
Data = 0
---------------------------------more troubleshooting--------------------------
-Disabled AntiVirus on both members
-Made sure DFSR TCP ports 135 & 5722 are open
-Installed all hotfixes for 2008 R2 (http://support.microsoft.com/kb/968429) and rebooted
-Ran NETSTAT –ANOBP TCP and the DFS executable results are listed below:
Sending Member:
[DFSRs.exe]
  TCP    10.x.x.x:53            0.0.0.0:0             
LISTENING       1692
[DFSRs.exe]
  TCP    10.x.x.x:54669        
10.x.x.x:5722          TIME_WAIT       0
  TCP    10.x.x.x:54673        
10.x.x.x:5722          ESTABLISHED     1656
 [DFSRs.exe]
  TCP    10.x.x.x:64773        
10.x.x.x:389           ESTABLISHED     1692
[DFSRs.exe]
  TCP    10.x.x.x:64787        
10.x.x.x:389           ESTABLISHED     1656
 [DFSRs.exe]
  TCP    10.x.x.x:64795        
10.x.x.x:389           ESTABLISHED     2104
Receiving Member:
[DFSRs.exe]
  TCP    10.x.x.x:56683        
10.x.x.x:389           ESTABLISHED     7472
 [DFSRs.exe]
  TCP    10.x.x.x:57625        
10.x.x.x:54886         ESTABLISHED     2808
[DFSRs.exe]
  TCP    10.x.x.x:61759        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61760        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61763        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61764        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61770        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61771        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61774        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61775        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61776        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61777        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61778        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61779        
10.x.x.x:57625         TIME_WAIT       0
  TCP    10.x.x.x:61784        
10.x.x.x:52757         ESTABLISHED     7472
[DFSRs.exe]
  TCP    10.x.x.x:63661        
10.x.x.x:63781         ESTABLISHED     4880
------------------------------more troubleshooting--------------------------
-Increased Staging to 32GB
-Opened the ADSIedit.msc console to verify the "Authenticated Users" is set with the default READ permission on the following object:
a. The computer object of the DFS server
b. The DFSR-LocalSettings object under the DFS server computer object
-Ran
ping <var>10.x.x.x</var> -f -l 1472 and got replies back from both servers
-AD replication is successful on all partners
-Nslookup is working so DNS is working
-Updated NIC drivers on both servers
- I ran the following to set the Primary Member:
dfsradmin Membership Set /RGName:<replication group name> /RFName:<replicated folder name> /MemName:<primary member> /IsPrimary:True
Then Dfsrdiag Pollad /Member:<member name>
I'm seeing these errors in the dfsr logs:
20141014 19:28:17.746 9116 SRTR   957 [WARN] SERVER_EstablishSession Failed to establish a replicated folder session. connId:{45C8C309-4EDD-459A-A0BB-4C5FACD97D44} csId:{7AC7917F-F96F-411B-A4D8-6BB303B3C813}
Error:
+ [Error:9051(0x235b) UpstreamTransport::EstablishSession upstreamtransport.cpp:808 9116 C The content set is not ready]
+ [Error:9051(0x235b) OutConnection::EstablishSession outconnection.cpp:532 9116 C The content set is not ready]
+ [Error:9051(0x235b) OutConnection::EstablishSession outconnection.cpp:471 9116 C The content set is not ready]
---------------------------------------more troubleshooting-----------------------------
I've done a lot of research on the Internet and most of it is pointing to the same stuff I've tried.  Does anyone have any other suggestions?  Maybe I need to look somewhere
else on the server side or firewall side? 
I tried replicating from a 2012 R2 server to another 2012 server and am getting the same events in the event log so maybe it's not a server issue. 
Some other things I'm wondering:
-Could it be the speed of the NICs?  Server A is a 2012 Server that has Hyper-V installed.  NIC teaming was initially setup and since Hyper-V is installed the NIC is a "vEthernet
(Microsoft Network Adapter Multiplexor Driver Virtual Switch) running at a speed of 10.0Gbps whereas Server B is running a single NIC at 1.0Gbps
-Could occasional ping timeout's cause the issue?  From time to time I get a timeout but it's not as often as the events I'm seeing.  I'm getting 53ms pings.  The folder
is only 3 GB so it shouldn't take that long to replicate but it's been days.  The schedule I have set for replication is mostly all day except for our backup times which start at 11pm-5am.  Throughout the rest of the time I have it set anywhere from
4Mbps to 64 Kbps.  Server A is on a 5mb circuit and Server B is on a 10mb circuit. 

Answer 1

I'm seeing the same errors, all servers are running 2008 R2 x64. Across multiple sites, VPN is steady and reliably.
185 events from 12:28:21 to 12:49:25
Events are for all five servers (one per office, five total offices, no two in the same city, across three states).
Events are not limited to one replication group. I have quite a few replication groups, so I don't know for sure but I'm running under the reasonable assumption that none are spared.
Reminder from original post (and also, yes, same for me), the error is: Error: 1726 (The remote procedure call failed.)
Some way to figure out what code triggers an Event ID 5014, and what code therein specifies an Error 1726, would extremely helpful. Trying random command line/registry changes on live servers is exceptionally unappealing.
Side note, 1726 is referenced here:
https://support.microsoft.com/kb/976442?wa=wsignin1.0
But it says, "This RPC connection problem may be caused by an unstable WAN connection." I don't believe this is the case for my system.
It also says...
For most RPC connection problems, the DFS Replication service will try to obtain the files again without logging a warning or an error in the DFS Replication log. You can capture the network trace to determine whether the cause of the problem is at the network
layer. To examine the TCP ports that the DFS Replication service is using on replication partners, run the following command in a
Command Prompt window:
NETSTAT –ANOBP TCP
This returns all open TCP connections. The connections in question are "DFSRs.exe", which the command won't let you filter for.
Instead, I used the NETSTAT command as advertised, dumping output to info.txt:
NETSTAT -ANOBP TCP >> X:\info.txt
Then I opened Excel and manually opened the .TXT for the open wizard. I chose fixed-width fields based on the first row for each result, and then added a column:
=IF(A3="Can not", "Can not obtain ownership information", IF(LEFT(A3,1) = "[", A3&B3&C3, ""))
Dragging this down through the entire file let me see that row (Row F) as the file name. Some anomalies were present but none impacted DFSrs.exe results.
Finally, you can sort/filter (I sorted because I like being able to see everything, should I choose to) to get just the results you need, with the partial rows removed from the result set, or bumped to the end.
My server had 125 connections open.
That is a staggering number of connections to review, and I feel like I'm looking for a needle in a haystack.
I'll see if I can find anything useful out, but a better solution would be most wonderful.