Linux DHCP issues are getting a problem. I have around 100 machines on the network where most of them are windows and some linux. If a client goes offline and then comes back most of the time there is a IP conflict.. I have never faced this issue on my home network though.
check in dhcp.conf Is there any static host definition in it. Allocate more than 100 IP in subnet range. And reduce the value of max-lease-time .