Weak Zigbee channel alert

Continuing the discussion from Release 2.3.9 Available:

I have received this alert and I know I can hit dismiss. I am actually thoroughly aware of the Zigbee problems on my network but am at a loss as to what to do about it or how I can rectify the situation that this alert is now flaunting. As stated below, I have attempted to make changes to my Zigbee network and have attempted to mitigate interference but I'm sorta at a loss as to how I can further troubleshoot.

Where to begin? I am not sure. So I'm just going to jot down a few things and hopefully someone can help me determine the fundamental question that I should be asking.

  • C-8 Pro hub and Zigbee sensors that fall off network repeatedly and haphazardly

  • Previously used a C-5 and then upgraded to a C-7 and never experienced Zigbee issues with either (except when I moved into the house with plaster walls (described below) my Almond Zigbee smartplugs suddenly became problematic and removing them immediately resolved the Zigbee issues at that time)

  • Attempts to change Zigbee channels and power levels produce no discernible benefits but now a change back to Channel 20 (having moved other Zigbee networks to channels 15 and 25 and 2.4 GHz WiFi to channels 1, 6 and 11) causes this new weak Zigbee channel alert

  • Zigbee channel scan indicates Channel 20 has the lowest RSSI numbers of all reported Zigbee channels and highest LQI

  • Zigbee Network Graph discovers 35/38 devices and shows the C-8 Pro has one child, one tentative connection to a non-repeating sensor and one neighbor (a SmartThings Zigbee Outlet) with that one neighbor (the SmartThings Zigbee Outlet) connecting to every single other zigbee device connected to the C-8 Pro's network on Channel 20

  • The Zigbee devices that cause the most issues are Aqara motion sensors and Aqara mini buttons as well as Hue indoor motion sensors and a Hue outdoor motion sensor and some infrequently used SmartThings buttons

  • Devices that have been rock solid include SmartThings motion sensors and Hue Dimmers

I include the following for full transparency:

  • My house has plaster walls (let me underscore that my house has plaster walls and I am acutely aware of the difficulty these plaster walls cause)
  • I doubt I fully understand the implications that my plaster walls actually have upon the wireless signals inside my house
  • I have a UniFi network (UDM Pro with two wired UniFi WAPs)
  • Sonos (the speakers) are temperamental sometimes as well

Having stated that, I'm unable to locate a solution for the Zigbee problems I've encountered since upgrading to the C-8 Pro amongst the topics I have read in the community. Some users seem to find that pairing Zigbee devices extremely close to the Hubitat Elevation has been successful. It is unclear to me if this is a panacea, though. Or if a panacea exists other than removing the problematic device (the C-8 Pro).