[OpenSER-Users] Loose route problem or misunderstanding

I'm having a problem using loose_route, and I'm not sure if it's a bug/feature/misunderstanding. I have a B2BUA (Asterisk) running on the same system as OpenSER, and in my failure_route for voicemail I direct calls there which actually sends them on to the voicemail server. If someone 'zeroes out' of voicemail, to be forwarded to the operator, the voicemail server issues a re-INVITE to redirect media. This is where the problem comes in. If I try to loose_route this re-INVITE, it fails. However, putting the B2BUA on a different system works fine. This is running OpenSER 1.2.3 currently, though I'm not particularly averse to upgrading to the latest 1.3.x if for some reason this is something that's been resolved there. Any suggestions? Thanks in advance, - Brad