Hi,
I think after updating to 18.7 I see on terminal screen:
syslogd: /var/log/suricata.log: Operation not supported by device
Did this came from update? 
Is this critical?
			
			
			
				Hi there,
Clear the log file once from the GUI under Services: Intrusion Detection: Log File and it should be back to normal.
Cheers,
Franco