I have been using an OBI202 for many years now with no problems, but recently the unit randomly disconnects and then immediately reconnects to my router. It is connected via an ethernet cable so it's not a WiFi issue and I have the latest firmware installed. I have also tried using a reserved IP address for the OBI device and still have the issue. The problem is not constant, but it occurs several times a day, every day. Has anyone experienced this problem or have any ideas on how to resolve it?
Have you checked that the ethernet cable is fully home in the socket at both ends? It is not unknown for the cable to be accidentally unplugged by someone who then reinserts it but does not know to push until it clicks. That can leave it in a state where small vibrations can cause the connection to come and go.
Also worth trying another cable.
Definitely check the cable, but also check that the router firmware is up to date. It also never hurts to power the modem and router down for a few minutes and restart. I too had a similar problem that restarting both seems to have solved.
Is the OperationMode on the OBi202 in router mode or bridge mode?