I think your case may have been a slightly different issue (or at least different to some of these cases, including mine – there could be multiple problems in this thread). In my case, the display on the OpenSprinkler indicates that it is trying to reconnect (as opposed to indicating that it’s connected and has an IP address), but it never successfully reconnects. So the OpenSprinkler unit is picking up that it has lost the connection… but the only way to do anything about it is to reboot the OpenSprinkler unit.
I have already set a fixed IP address for OS on the router, so that has not been a solution for the problem I’m encountering.