Zigbee devices keep going unresponsive

It's not the Iris V1 that's the problem, it's the ZLL bulbs. As a general rule, Zigbee HA devices should never be on the same mesh network as ZLL repeaters. It just causes problems in your mesh eventually. You're going to see problems with all ZHA devices if you have ZLL bulbs on the network also, not just Iris v1 devices.