asterisk users - May 2011 - DTMF digits received, but not completely forwareded

Hello,

we are running an Eicon Diva Server card with chan_capi
and Asterisk-1.4.8.

When we put in capi.conf softdtmf=off, the local command
"read()" is recognizing dtmf digits from cell phone and from
ISDN phones and from VoIP phones (via PSTN) very well,
and asterisk is forwarding those digits correctly and
completely to other switches via SIP.

However, when an old analogue telephone is sending the
DTMF digits, they are recognized approx 60% only.


Even more strange:
When we put softdtmf=on (relaxdtmf=off), the local command
"read" is correctly recognizing _almost_any_ incoming DTMF
digits from the Diva card.
This is the desired behaviour, which we would like to
keep.

However, when the "read()" is running on another asterisk box,
and the call is switched to that box using Dial(SIP/....),
only 80% of the digits are arriving at the other box.

We tried with RFC2833 and with INFO (on both sides same).
No difference.

Can anyone please give me a hint, why not every digit,
which the first box would recognize with "read()", is
forwarded by SIP to the other box?
Why that difference?


Roger.