TCPS-123 — The parent process tried to signal its children and received an error
The parent process asks its child processes to perform some actions by sending them signal SIGHUP (the concrete type of the request is determined by a flag set by the parent in the scoreboard - the shared memory used for communication between parent and child processes).
This message means that the signal cannot be sent and thus at least some children will not perform the requested action (changing log level or exiting).