MQTT on 2 Arduinos

Hi,
I am trying to make me an intelligent home and I need 2 Arduinos connected with a MQTT broker to do that. The problem is I cannot make them both work at the same time. When I plug in one of them to power and my router everything works fine, but when I plug the second one this one works fine, but the first one doesn't read from the subscribed channels. It makes posts to the broker, but doesn't receive any updates from it. When I restart it it starts working fine but then the second Arduino gets jammed the same way. I have changed the MAC addresses and IPs for both Arduinos. Can someone please advise?