Yeah it still sounds like you doing the opposite from following these best practices tips:
Those type of symptoms are common indicators of EMI/RMI/EMF-interference and/or poor reception.
The first thing you need to know is that all Zigbee radios can be extremely sensitive to EMI/RMI/EMF-interference, and the second thing you need to know is that a Zigbee network’s range/coverage depends heavily on mesh networking by design because Zigbee radios use low-power and high-frequency radios have very week signals with poor propegation (crappy penetration of building materials). Those two combined can create the perfect storm, so you really need to take preventive actions to both avoid placing Zigbee devices too close to sources of EMI/RMI/EMI. Read and follow these best practices:
The most important preventive actions to take in order to avoid the first is to connect the Zigbee Coordinator USB radio dongle via a long shielded USB extension cable to a USB 2.0 port of USB 2.0 hub and keep it away from USB 3.0 devices/peripherals/cables, and to prevent the second you want to begin by also add many always-on/always-connected/always-powered mains-powered Zigbee devices at strategic locations in your home that act as “Zigbee Router” devices (sometimes also referred to as Zigbee Range Extenders or Zigbee Repeaters) before adding any Zigbee End Devices (which include all battery-operated devices as we.ll as a few mains-powered devices too, which is especially common if they do not need neutral or if they are a lightbulb)
Other than that you as well need to replace batteries with fresh ones in any battery-operated devices.
Again, read and try to follow this → * Zigbee networks: how to guide for avoiding interference + optimizing using Zigbee Router devices (repeaters/extenders) to get best possible range and coverage
After followed all that advice then try re-pair the device again before doing any deeper troubleshooting.
Also suggest try upgrade to the latest unofficial community Zigbee (NCP) firmware build on your Zigbee Coordinator radio adapter, nothing that if you have a Sonoff Zigbee from ITead then remember that there are two different Sonoff Zigbee 3.0 USB Dongle Plus models (“ZBDongle-E” based on Silicon Labs EFR32MG21 radio SoC and “ZBDongle-P” based on Texas Instruments CC2652P radio SoC) that uses different firmware builds.