I have seen those from time to time . epically if if using park Wi-Fi and there are so many clients that someone is manually assigning an I/P address.
It can also be a clue that someone is trying to hack.. Just so you know. (But then so can most all error messages save 401).
On my netowrk the router has an IP address for chatting with the park.. And each device chats with the router on either a pre-set manually programmed IP address OUTSIDE the DHCP range or on a DHCP dynamically assigned address. no conflicts in quite some time.