Under the suggestion of @Water_my_lawn, I substituted EthernetENC with UIPEthernet (version 2.0.12) and recompiled the firmware, numbered 2.1.9(10) (i.e. 2.1.9 minor revision 10). So the only difference between minor revision (9) and (10) is the Ethernet library. The firmware is available for OpenSprinkler hardware 2.3 and also 3.2 with wired Ethernet connection. (It’s irrelevant if you use OpenSprinkler 3.2 only in WiFi mode). In any case, if you are on 2.1.9(9) and having frequent lockups or disconnections, give 2.1.9(10) a try and see if it solves the issue. The matter of fact is that we don’t know why some users are encountering problems with (9), we have not been able to reproduce the issue ourselves so without seeing the problem happen we can’t really debug it. I think it’s unlikely the same firmware works for all users (I am sure some users would have problem with (10) as well), so while no single firmware works for everyone, hopefully between (9) and (10) one of them will work for you.