The MWG-to-DC connection is a long running connection. It should also be very chatty as anytime a user authenticates, MWG must talk to the DC (assuming proxy auth is in use).
Shot in the dark but, 900k is a lot of times to be disconnected in 5 hours, I'm guessing its not a timeout... Perhaps there is an IPS in between and it sees SMBv1 traffic, and resets the connection.
With MWG version 7.8, SMBv2 is used for MWG-to-DC communication. I believe there is discussion on-going to have it backported to older versions but I dont have a timeline on that.