> In that case it suggests it is some setting you have applied to the
> phones that is causing it.
I just called Aastra tech support. I’m always VERY impressed that the
first person who picks up the phone is very technical. He said that they’ve
had reports of this issue. The problem goes away when “sip rport: 1”
is removed. Even though the manual says that it’s “recommended” for NAT,
it isn’t needed and is causing this problem. They appear to be treating
this as a bug.
(There’s supposed to be a new version of the firmware very soon, since it’s
ready, but just not on the web, but it won’t solve this issue.)