[Users] (PR)ACK problem with uac_replace_from

I seem to have an issue with uac_replace_from. I am using openser as a media proxy. For invites I replace the numbers with leading 0's with 61 for Australia and forward the call to our LCR box which then forwards the call to the correct voice to pstn gateway. I am trying to use uac_replace_from to set the from address so the callerid appears correct on the outgoing calls. This seems to work fine for the INVITE request, but on subsequent PRACKs and ACKs (which just get loose routed), something strange happens to the from address. On invite, the From get re-written: From: Jeff <sip:610089001@proxy.sipone.com;user=phone>;tag=1790577941 to From: Jeff <sip:0892209080@sipone.com>;tag=1790577941 For the PRACKs and ACKs, this happens: From: Jeff <sip:610089001@proxy.sipone.com;user=phone>;tag=1790577941 to From: Jeff <\032\317\352S\232\222B\230\234K\231*BV\300\030\303\332\ah\303\306i\365\005\016\200\250\000\000\230\016\200\252j\200\002`\000\000\016>;tag=1790577 941 There shouldn't be anything happening to the From address on the (PR)ACKs at all. Anyone have any ideas? I have attached a ethereal dump of the call setup. Jeff