Is there a way to submit a bug report on a R7000 router?
Defining a specific address for a MAC addres should cancel any existing DHCP lease that the MAC address has. It doesn't, so the newly defined IP address does not take effect until the existing lease expires. Reboots or DHCP renews from the client do not change the IP address.
Since the lease expiration time is long (longer than 24 hours), this make reconfiguring devices really time consuming.