Environment:

• All devices being the RainMachine, Laptops, Desktops, Android are on the same subnet
• I repeated all tests with Remote Access enabled and disabled
• Laptops/Desktops are a mix of wired and WiFi connected
• I have a single SSID on my WiFI AP, and it is using only the 2.4GHz radio
• This is a simple, flat, L2 network
• I primarily use the Android app, set for direct access using IP address and :8080
• For years, I've had zero connectivity problems until recently

Problem:

• I noticed the Android app was unable to connect to the RainMachine
• I tried several Laptops/Desktops, and they were also unable to connect

Troubleshooting:

• Ping from Laptops/Desktops/Android gets no replies
• Checking the RainMachine front display shows WiFi connected, the correct IP address, SSID, etc. etc.   The only Failure is the HTTPS Call related to NOAA
• I rebooted the RainMachine while running continuous pings from several devices and after a few min, all show ping responses.
• nmap scans show ports 80, 443, 8080, and 8081 open
• I could connect from my Laptops/Desktops without issue
• My Android could connect via a browser, but not via the app
• After a random period of time from few minutes to hours every device once again lost all connectivity to the RainMachine
• I feared the RainMachine was simply dying a slow death 

Weird workaround:

• On a whim I enabled OpenVPN on my Android which assigns an IP from different subnet, and the app worked just fine

• Seeing that a routed connection worked, I modified my firewall rules to allow my DMZ subnet to reach the RainMachine.  Pings and nmap scans from the DMZ devices worked just fine, while they had stopped completely from all devices on the RainMachines local subnet
• The RainMachine was not and is not dead, it is simply refusing connections from the local subnet after some period of time while routed connections work very reliably

Questions/Concerns:

• Why do routed connections from an alternate subnet work reliably while local, non-routed, connects fail after some period of time?
• IMO this is HIGHLY unusual, and suspiciously coincidental with the recent turn towards a subscription model