Is not something like
do {
err = sys_notify_fetch_result(&cli.notify, &res);
if (!err && res) {
LOG_ERR("Clock could not be started: %d\n", res);
return;
}
} while (err);
missing in https://github.com/nrfconnect/sdk-nrf/blob/master/applications/serial_lte_modem/src/main.c#L227 ?
Error return code should be handled also after github.com/.../main.c