ACME Packet sends 404 instead of 503 when using local route table

I have a local policy configured with 3 next hop destinations to try for inbound calls.

Next-hop 1 = Local route table

Next-hop 2 = IP PBX

Next-hop 3 = Local backup GW for IP PBX

The SIP interfaces for these routes are tied to the same physical interface on the SBC. What we are seeing is, when the phy-interface is down and non of the next hop SA's are available, the responds with a 404 not found instead of a 503 service unavailable, which is require by the carrier to trigger a failover on their side.

Looking through the sipd debug logs, I see the LRT lookup returns a 404 not found if it does not find a number match and it seems like the SBC uses this as overall response code when no routes are available.