For a long time I had problems with 2 zigbee plugs. They would fail to report their status or simply stop responding completely. I could not figure out what was the problem with them. Especialy since I have other plugs of the same model placed even farther then those 2 troughout the house and they work fine. This was driving me nuts until I was fidling with another device in the vicinity, but totaly unrelated to my HA:
That device had a USB memory stick pluged into it. As soon as I remove that USB stick, my problematic plugs started to work and they are doing fine since then.
Sometimes we try all sort of solution like boosting signal, blanket the house with repeaters, moving things around, replacing device with a different model and we forget about the unconspicuous little thing whitch can cause lots of interferences.
Yes USB 3.0 and 2.4 GHz does have some issues so much that ASUS and some other router brands had to de-tune their USB ports not to interfere with their Wifi signals. Zigbee also uses the 2.4 GHz spectrum so your solution of moving the USB allowed the signals to reach the device.
I had the same with a new monitor that contained a USB C/USB 3.x hub in it and a Samsung button I kept on the desk. The hub would prevent the button from working. Had to move the button to another location.
