at2 DLR weirdness

  Hi list,

I have the following setup:
-A Wavecom GSM modem connected to a linux box, running kannel 1.2.1 
(stable) compiled by hand
-An EMI SMSC connection

The goal is to monitor the SMSC connection with the GSM modem.
For this, I send a specific keyword with the modem,  and I wait for the 
answer.
In order to make the tests more reliable, I use a dlrmask=31 when I send 
the MO,
so our monitoring don't shout for a stupid network problem.
This part works almost fine, but the success isn't as accurate:
Sometimes when I send an SMS with the modem, I got a DLR call with a 
value of 1
which should mean that the MO has been delivered. Before the 
dlrvalue=1,  I can
have a DLR call with dlrvalue=8  or dlrvalue=4.
The fact is that these messages never came to my servers, and I have 
incomming traffic.

What do you gentlemen think it can be? There are so many point of 
failures that I can't
figure it out... For me the bug can come from :
- Kannel at2 driver / dlr handling
- The GSM modem
- The operator SMSC

Thank for your precious time and knowledge...

Mat.