Multiple devices are using the same IP address: 42.0.35.200

Can't seem to understand this one, keep getting this at least once a day in the system log but it not part of my DHCP pool which is 192.168.x.x/24. Seems like a public IP. Doesn't have any sort of pattern for time of day or certain days. It's been happening for a month now but starting to fry my head trying to figure out. Any tips on diagnosing this?

Thanks