Attached is an image showing the wireless log which shows that the devices and duration of connection. It looks like the total connection time overall not current connection time.
In a nutshell - the noise from USB 3.0 interferes with the 2.4 GHz signal. However, the wireless industry is proactive about the problem. Just about all of the router makers I spoke with that offer routers with USB 3.0 ports have those ports shielded to alleviate that interference
Stumbled across this thread. I am having somewhat similar issues with the 2.4Ghz from my AX11000. I am unable to manually connect to 2.4Ghz on my iPhone when I force it to use 2.4Ghz. Also, other devices which use 2.4Ghz exclusively (robot vacuum, garage door) are not connecting. Another symptom is that even 5Ghz connections will drop off occasionally.
Unfortunately, I cannot recall when this started. My AX11000 was moved to a temporary location whilst we do some renovations in the house--it is possible the problem started close to when the AX11000 was relocated. My AX11000 is the center of a mesh set up with 4 X ZenWiFi nodes set up in AiMesh. So this is a deviation from the Andrew_2468's scenario. Each of the nodes is using wired backhaul so they are each connected to the AX11000 not piggybacking from one to another like they might using wireless backhaul. I find it difficult that all 4 of the ZenWiFi nodes is having trouble transmitting 2.4Ghz--I would not expect a problem with the AX11000 to be affecting the transmission of signal from the nodes.
I have done a full factory resent of the entire Asus network environment and the problems still occur.
I have since installed a Netgear Orbi WiFi 6 mesh router + 2 satellites in parallel to my Asus set up. All of my devices (phones, robot, garage door opener) are connected to the Orbi network without problem and is very stable.
I have limited options to locate the AX11000 during my renovations but may try to find another location.