'connection reset' means that a "bad" tcp disconnect occurred, not a graceful close.
SS read, this is the connection to the set and the failure occurred when we tried to read data from the connection.
so, either a problem between mbg and the isp, a problem between the set and their isp or a problem with the internet.
Since you're in a DMZ, with a separate f/w in front, maybe grab tcp captures on the inside and outside interfaces for mbg's ip, port 6801 and see if it's a 'real' problem of if your f/w is mucking things up (it happens, checkpoint is famous for it).