Change in code unit error handling with 2013 R2?

We have several code units that connect to managed .NET dlls. Inside those code units, we throw errors and expect .NET to catch them. This worked in 2009 and 2013, but broke with 2013 R2.

Previous behavior:

Code unit would hit a condition, throw an exception to .NET and continue.

Current behavior:

Code unit hits the condition, throws the exception, but the NAS shuts down as if it were a fatal exception. our .NET dll catches it, but gets disconnected from the server and our application halts.

Code Unit Sample:

ERROR('Add the ' + TableName + ' table to the Validation Rules table.');

Did the behavior of this ERROR keyword change between 2013 and 2013 R2? Is there a better way to do what we're trying to do without killing the NAS service?