Record Route in 200 OK are overwritten with SA's IP in ACK response

I'd appreciate any assistance with this...

 

I have an egress call flow to a upstream provider ( Softswitch-->Acme 4500-->Vendor). Upon reciept of the 200 OK/SDP, which includes record routes;

 

Record-Route: <sip:a.a.a.a;lr;ftag=10.152.1.13+1+2b42023+2b049182>
Record-Route: <sip:b.b.b.b;lr;ftag=10.152.1.13+1+2b42023+2b049182;did=d56.09941417>
Record-Route: <sip:c.c.c.c;lr;ftag=10.152.1.13+1+2b42023+2b049182>

where c.c.c.c in the IP that received the original Invite.

 

The ACK response is rewriting the IP's in the Routes;

 

Route: <sip:c.c.c.c;lr;ftag=10.152.1.13+1+2b42023+2b049182>
Route: <sip:c.c.c.c;lr;ftag=10.152.1.13+1+2b42023+2b049182;did=d56.09941417>