The log indicates your rpi’s network has become unreachable.
Next time your SatNOGS goes ‘offline’, login into the pi at the terminal and trying pinging one of Google’s nameserver IPs
If it times out, your network connection has indeed dropped and you’ll need to troubleshoot your wifi connection or wired connection to your router. Rebooting your pi fixes this temporarily (by resetting your pi’s network interface and forcing a renegotiation) but as you noted it will occur again.
If it doesn’t time out and pings successfully, it could be related to a DNS lookup issue on your LAN. You might need to hard-code some alternate DNS servers in place of relying on your router to be the primary DNS for your LAN.