Route Header, and DNS

Hopefully I've hit the correct group for this.  We recently experienced a problem that's got me wondering how the SBC handles the Route header.

 

UA's that were registering to one of our 4500s fine for months, suddenly stopped registering without any changes to the Access or Core realms it uses.  Other UA's on this interface are unaffected.  The difference being in signaling, the affected UA's send a Route header with the FQDN of the SBC Access interface.  Instead of the ACME recognizing that this resolves to an IP on itself and passing the packet, it started routing the packet out a Core interface back to the Access interface.  I'm assuming it was a bug from our old code, just odd it came out of