Core Reports Duplicate IPs

The log in my core has been reporting a lot of duplicate IPs. We have 1000+ people on our network with a variety of BYOD devices. Every device is obtaining an IP from the DHCP server, which according to our systems admin nothing is wrong with the DHCP server. I need to find out why devices are obtaining an IP addresses that are already in use, and how I can minimize these duplicate IPs.
Please let me know if I need to be more specific.