when calls made outbound, the ringback have echo, and not all ringback tone, for example:
it is a total of 5 ringbacks to an example number,
out of that 1, 2 have echo, then 3, 4 not, and echo on 5
and it changes that order with other attempts to the same number.
already tired vad no vad, echo cancel coverage, reset the router, the port..etc
the router is a 2811, and they are nortel phones, no ccm here, running 12.4.6.t6