Device on LAN ports abusing DHCP DISCOVER request

[Geofferey]

My router is an RT-AC68U. I have a Windows 2008 R2 server serving DHCP request and a Zmodo NVR with a manually assigned ip attached directly to the LAN ports on back. The problem I am facing is due to the NVR spamming the network with DHCP DISCOVERs on the broadcast which causes the DHCP server to reply with DHCP OFFERS that spam the network and drain the battery on some of my mobile devices. I have tried blocking DHCP from the source mac of the abusive device using EBTables to no avail. The DHCP DISCOVERS still reach the server and it replies even if I block all traffic from it's source mac. I can keep this traffic from leaking out of the wireless interfaces but can't stop it from propagating across the LAN ports to the DHCP server. My question is how can I stop the DHCP DISCOVERS from escaping to the server from the NVR?