We were performing a rather massive set of updates. During these updates, one of the secondaries began to show SEND_ERROR messages in the logs, and also began to lag behind the primary. The CSHARP client was not catching the errors, causing everything to be inoperable from a client standpoint.

The only values that show up in the logfiles are:
2016-08-17T10:53:57.994-0500 I NETWORK [conn886174] SocketException handling request, closing client connection: 9001 socket exception [SEND_ERROR] server [webserver:55640]

– I will also file a report on this with the CSHARP crew, as it appears to be unhandled coming back to the client.