Mario YO2LOJ has found a small bug in the source code of UROnode.
Thanks to Marius YO2LOJ for a patch in do_ports within command.c where there is a possibility that the interface count may return NULL and the function will generate an exception in libc for the routine causing the node to segment fault out and disconnect the user from the node.
To patch the bug you need to edit the command.c in the source code of UROnode.
On line 398 you will find this line.
if (strcmp(ax->dest_addr, "*")!=0 && strcmp(ax25_config_get_name(ax->dev), cp)==0) n++;
You have to replace it with this.
if (strcmp(ax->dest_addr, "*")!=0 && ax25_config_get_name(ax->dev) && strcmp(ax25_config_get_name(ax->dev), cp)==0) n++;
After that you can recompile the source.
Or you can download a complet command.c here.