I have been doing quite a bit to get my environment totally stable since posting this and have put together some easy to reference notes so here goes. Maybe they should be added to the official documentation but not my decision.
Zigbee and WiFi Interference
The 2.4 Ghz band is shared by Zigbee and WiFi and interference can occur. The channel settings for each should be set to provide as much separation as possible to avoid this interference.
WiFi and Zigbee channels are not the same, WiFi Channel 11 is not the same as ZigBee Channel 11 as shown in the chart below.
For the US setting Zigbee to 11 and WiFi to 11 or Zigbee to 25 Wifi to 1 would be good choices for separation.
A WiFi analyzer app on your Smartphone will help find a good channel without interference as exampled. There are several good free ones available. Note that you will not see the Zigbee in the analyzer.
You will need to find and set the control channel in your router and do not rely on “Auto” configuration as most will not detect the Zigbee interference.
You may or may not be able to change the channel on your Zigbee controller or devices so you will need to do some upfront research on what the channel settings are or how to find them and can they be changed.
Something else to be aware of is if you have multiple Zigbee hubs. Beside a Conbee I have a Lightify Hub and there is no way to manually change the channel or easily know which it is on. Hubs similar to this “find” the channel with least interference automatically at startup. Once you separated your WiFi and Zigbee on the devices you can control if you have other hubs you cannot control power them down completely for at least 15 minutes or so and then power them back up. Keep them at the furthest distance from each other you can. The hub should reset to a channel that works with the changes you have made. For best results get everything on to one Zigbee controller that you can manage if at all possible to avoid this situation.