I am reviving an old problem…
My Rachio 3 will every day go completely off-line and unresponsive. There are NO lights visible on the front and the controller can only be recovered by power cycling.
I am convinced this is a bug in the underlying wifi networking system of the controller - which I guess it is some version of embedded Linux. I have a NetGear mesh ORBI network, and to resolve the original problem I had years ago I gave the Rachio a fixed DHCP IP. This worked for about 2-3 years. The controller would very rarely go offline.
However, I recently I moved one of the ORBI satellites to a new location much closer to the Rachio. Almost immediately the controller started “crashing” every day. The Wi-Fi signal is pretty strong ( 200mbps at the controller). However, the controller is now equidistant from two satellites. I think the wi-fi subsystem has some issue. I have 30 other wifi devices both on 5Ghz and 2.4Ghz that never give any problems. The Wifi Network is solid. I have now dedicated a “smart switch” to power cycle the controller every day before any watering so I can at least have it functioning reliably.