I have been seeing a problem starting 9/9/2015, possibly due to the latest update being rolled out as mentioned elsewhere, where the Relay Response URL set in the x_relay_url param for SIM transactions is getting transformed into all lowercase.  Monitoring our http server logs, I see the Relay Response URL being requested from Authorize.net's server after the customer pays, but due to it being all lowercase, it is ending up in a 404.

This is causing a major problem for us as we keep track of our customer's payments and update the status according to the Relay Response.  The effect of this is that no current payments are ending up getting marked as successful on our end.  

Again, it looks like the Relay Response URL parameter contents for SIM transactions is getting translated to all lowercase, which is breaking processing on it.

Is this a bug, or the new intended behavior?