I tested it for REGISTER, and it seems to break if the registrar sends e.g. a 4xx with no contact back, causing the log line
ERROR: topos [tps_storage.c:1407]: tps_db_load_dialog(): invalid dlg uuid provided
Is this something you've experienced, @toharish ?
Thinking of it: if the Contact is not handled by topos, where is the lookup key `cparam_name` stored? Could it be that this only works with `contact_mode=2`? If so, could you please provide a full example to reprooduce it?