Zigbee is extremely sensitively to EMF/EMI/RMI interference so normally I advise connecting the Zigbee Coordinator adapter via a long USB cable (shielded USB 2.0 extension cable) and not placing it close to any USB 3.0 ports/devices/peripherals as those are infamously known for interfering with Zigbee RF signals, but since you have a Raspbee which is an internal Zigbee radio module (which can not be moved and is based on an older radio chip) I am also going to advice you to start by buy a new Zigbee Coordiantor USB dongle that is based on a more modern Zigbee radio chip, such as example ITead’s Sonoff ZBDongle-P (USB radio adapter based on CC2652P and with an external antenna) → ITead's "Sonoff Zigbee 3.0 USB Dongle Plus" (model "ZBDongle-P") based on Texas Instruments CC2652P +20dBm radio SoC/MCU
Arguments why posted in my reply to this other thread → Zigbee buyer's guide
Anyway, it is really easy to migrate if you have already upgraded to a later deconz firmware on your existing RaspBee/ConBee → https://www.home-assistant.io/integrations/zha#migrating-to-a-new-zigbee-coordinator-adapter-inside-zha note that need have first manually upgraded firmware are needed to export Zigbee network data from the RaspBee/ConBee chip to a backup file → https://github.com/dresden-elektronik/deconz-rest-plugin/wiki/Update-deCONZ-manually
In addition, you really need to make sure that you have enough “known good” Zigbee Router devices (a.k.a. Zigbee siganl repeaters / Zigbee range extenders) between your Zigbee Coordinator and this or any other devices that are having issues. Zigbee has poor range and depends on having many Zigbee routers in its Zigbee network mesh to relay messages.
I highly recommend that you read and try following all the tips here before troubleshooting any further → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
Not going to ask if you have replaced the battery and instead just state that you will need to replace the battery more often if you have issues with interference or lack of Zigbee Router devices as the messages will need to be resent if the Zigbee Coordinator or any devices have poor reception or are placed close to noise sources.