We are intentionally using a 304 response but the error logged in Honeycomb is

System.InvalidOperationException: Writing to the response body is invalid for responses with status code 304.

I guess we're abusing 304 if we are using it with a response body:

return StatusCode(StatusCodes.Status304NotModified, editGuid);.

Perhaps we shouldn't use 304 for a "successful" response, even if the success is that no changes were name so nothing had to be done.