I would search the community, there are many threads out there from people troubleshooting these types of issues. Basically, you want to look at the Zigbee logs, not the Hub logs, found in the Zigbee settings. Look for unresponsive devices making no logs, and for very busy devices that are constantly churning out logs, that may be spamming the network. They are only live logs, so you have to watch them. You can send commands to devices to see in the logs how they react.
You might also want to install the Zigbee Map app to get a better visual and more info about the mesh.
