Suggest starting by reading and trying to follow all the best practice tips here → https://community.home-assistant.io/t/guide-for-zigbee-interference-avoidance-and-network-range-coverage-optimization/515752
I also highly recommended migrating to a newer Zigbee USB adapter (as Zigbee Coordinator radio) and connect it via a longer USB-extension-cable to a USB 2.0 port (not USB 3.0 port) instead of using an internal GPIO adapter like RaspBee (which will be more affected by interference than external Zigbee Coordinator adapters), especially if have any other USB 3.0 devices connected to the same computer.
In addition, use disable WiFi and instead use wired Ethernet to your computer for Home Assistant, as well as consider adding more Zigbee Router devices and maybe even buy a few dedicated Zigbee repeater / range extender devices to add to your Zigbee network to help it better optimize its mesh network functionality.
In essence, with Zigbee you need to understand that it is very important always keep in mind that relatively speaking Zigbee radios are extremely sensitive to interference. So simply adding more mains-powered devices that act as Zigbee Router devices and do everything to avoid interference will usually resolve most issues or at least hide many symptoms of noise environments in the same frequency range.