That exact problem and scenario is covered and explained in the guide I already linked to → Zigbee networks: how to guide for avoiding interference + optimizing using Zigbee Router devices (repeaters/extenders) to get best possible range and coverage
…including reference to this whitepaper → https://www.usb.org/sites/default/files/327216.pdf as well as to this blog post → 2.4GHz Intra-System (or Self/Platform) Interference Demonstration - Unit 3 Compliance
Always use a long shielded USB extension cable to get it far away from all other electronics/appliances or electricity, and if your computer does not have a USB 2.0 port then the recommendation is to connect to buy a powered USB 2.0 hub, (yes you can alternatively just use a USB 2.0 extension cable as that will also convert it to USB 2.0 but the shielding in cables made for USB 3.0 is much better and it is hard to find USB extension cables with good shielding so it is more practical to just buy any long shielded USB extension cable and simply connect it to powered USB 2.0 hub or directly to a USB 2.0 port if your computer has one).
Zigbee interference avoidance and network range/coverage optimization
Interference
Before you get started with Zigbee, or at least before starting troubleshooting any issues with Zigbee, you should be aware that all Zigbee devices, and especially the Zigbee Coordinator, can be extremly sensitive to EMF interference, and practically all sources of Electromagnetic Interference (EMI, also called Radio-Frequency Interference or RFI), are infamously known for sometimes leading to serious Zigbee transmission/reception loss or connection problems. Therefor you should always take the actions suggested in this guide to avoid keeping any sources of EMF/EMI/RMI interference close to the Zigbee Coordinator adapter or vice versa!
Symptoms
Symptoms of radio and electromagnetic interference commonly show themselves as reoccurring intermittent failures and errors when sending or receiving Zigbee messages/signals and can cause anything from significant communication problems to weird issues and random degradation in performance that either permanently or temporarily prevent devices from communicating properly with the Zigbee Coordinator, or sometimes even completely block/stops all Zigbee communication.
Sources
While Wi-Fi routers and WiFi access-point are probably the most well-known sources of interference, you need to understand that all electric devices/appliances, especially computers and computer peripherals, do generate electromagnetic interference (also known as EMI/EMI/RMI, or signal noise in layman’s terms) , which can jam or interfere with signals transmissions on the 2.4 GHz radio band frequency, and degrade the wireless communication with your Zigbee adapter/devices.
For example, interference from USB 3.0 ports and unshielded USB peripheral cables are especially infamously known to affect 2.4 GHz radio reception for low-power/low-bandwidth devices. Therefore you should always place your Zigbee adapter far away as possible from any potential sources of EMI/EMI/RMI, preferably by using an adequately long shielded USB extension cable connected to a USB 2.0 port.
Home Assistant posted a video to clearly show Zigbee’s symptoms with electromagnetic interference:
