Recommend moving all Zigbee devices to the same Zigbee network if possible, but note that since those are Zigbee Router devices you need to make sure that they are always powered. Do not make the mistake of connecting Zigbee Router devices to dumb switches so that they get disconnected as that will make your Zigbee network unstable or at least unreliable.
Highly recommend that you read and follow these community guide which if you follow the advice/tips normally resolves most common setup issues that can cause instability or weird and intermittent problems → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage