Hi again - I have to apologize, because I was incorrect in previously stating that Zigbee routers count towards the 32 device limit. That limit is only for end devices as stated here.
However, you will only be able to pair one more end device that directly connects to the hub, and after that any additional devices need to connect via a router. Since you have so many devices directly connected to the hub, perhaps moving a router closer to the location of the hub would help with your issue of dropped connections - if they are due to weak network connections because of distance and or interference.