AVAYA IPO 500 v9.0.316.2 with 5 SIP trunks.
That is a private build, meaning, there was an issue, and a patch was created. i can not check to see if the bug was worked into the next SP or GA build.
BUT, if i were you, i would open a service ticket, as we dont know the ramifications of the private build on your issue.
Also, if the fact that it is using 2 SIP trunks for twinning is an issue, then you might want to upgrade to R10, as they built that into R10. (ability to do a centrex type transfer on SIP, if the provider supports it)
