Before doing any deeper troubleshooting I suggest that you begin to rule out both EMF interference (which can cause symptoms like you describe) as well as lack of routes due to having too few Zigbee Router devices. Ruling out those first should make troubleshooting much easier and less frustrating.
Recommend read and follow these tips → Guide for Zigbee interference avoidance and network range/coverage optimization
Especially be sure to connect the Zigbee Coordinator adapter via a long USB extension cable to a USB 2.0 port (and not a USB 3.x or USB 4.x port ). Zigbee devices are very sensitive EMF/RMI/RMI interference and have a relatively short range and these are the most common root causes for this.
Also add a few mains-powered Zigbee products that are known to work as good Zigbee Router devices (e.i. Zigbee signal repeater/extender) to act as the stable backbone of your Zigbee network mesh. Generally, the more Zigbee Router devices you have the more stable your Zigbee network mesh should become.