Hi Roch,
my immediate response is that I don't really know what's the cause. We are testing the SCCPlite interface of osmo-bsc in our automatic tests every night, so I presume it's not fundamentally broken but maybe just some unexpected differences in configuration.
The config file used in the tests can be seen at http://git.osmocom.org/docker-playground/tree/ttcn3-bsc-test/sccplite/osmo-b... while the test suite (simulating MSC) uses this config: http://git.osmocom.org/docker-playground/tree/ttcn3-bsc-test/sccplite/BSC_Te...
Maybe this helps to spot the differences? In case of doubt: * is there anything TCP/IPA at all? * can you post your config (at least the related sections)?
Regards, Harald