Setting mask_callid should not be needed, was mistakenly checked in the intermodule API function. I pushed a commit (referenced above) to remove it.
If it is that easy to reproduce, once it happens, trigger printing of memory status in the syslog and then paste the corresponding log messages here. See:
- https://www.kamailio.org/docs/modules/stable/modules/corex.html#corex.rpc.pk...
To make it easier, set `childred=1`, reproduce and spot the pid of the process printing the out of memory message. Run the above rpc command for that pid. You still need to send some SIP traffic to get the command executed, because it depends on next processed packet.