Got reject for frame , retransmitting zt_pri_error problem


Recently we changed our pri provider and they asked from us to enable echo cancellation.
We have asterisk (1.4.21) with digium E1 TE205P, but without hardware echo cancellation - so we enable the soft - and many times (for outbound calls) - the agents receives the message that the number is busy - but that is not true - and another times echo in the line.

log files:
Many Messages of "zaptel Disabled echo canceller because of tone (rx)"
and after sometime:
“timing source auto card 0!
wct2xxp: Clearing yellow alarm on span 1
Zaptel: Master changed to TE2/0/1
wct2xxp: Clearing yellow alarm on span 2”

Any idea ?