My Rachio 3 recently started dropping its Wi-Fi connection regularly. It had been working well for the past 2-years with rock-solid connection to my home Wi-Fi network. I followed all of the troubleshooting advice online (e.g. unplug/replug, reset, confirm 2.4GHz network connection, etc.) but without any success.
I have Verizon Fios 1GHz internet service at my home: CR1000A Wi-Fi 6E router, and recently purchased & installed their CE1000A Wi-Fi 6E extender to establish a Tri-band (2.4 / 5 / 6GHz) Self-Organizing (mesh) network. I enabled the Router/Extender to broadcast a separate IOT (2.4GHz) SSID so I could connect IOT devices that require 2.4GHz wireless – like the Rachio 3.
What worked for me: in Network Settings (1) ensure that the Router and Extender radios are broadcasting on the same channels (e.g. pick the same 2.4GHz channel AND bandwidth values on BOTH the Router and the Extender, pick different 5GHz channel and bandwidth values and set them to be the same on BOTH the Router and the Extender, pick different 6GHz channel and bandwidth values and set them to be the same on BOTH the Router and the Extender), (2) ensure that the 2.4GHz width value is set to 20MHz – mine was set to 20/40MHz by default, (3) reconnect the Rachio 3 to the Wi-Fi network, and (4) set a Static lease type for the Rachio 3 in the IPv4 Address Distribution section to get a static IP address for the Rachio 3.
My Rachio 3 has NOT dropped its connection for 3-days since I made these changes. I think the significant change was switching the 2.4GHz bandwidth value from 20/40MHz to 20MHz.
Hope this helps if you find yourself in a similar situation.
More importantly, my Rachio 3 is still online for the past week.