I have two 2TB Time Capsules attached to a network through a Netgear router. Each Time Capsule is connected via Ethernet with the WiFi set to "off".
Each Time Capsule is assigned a unique static IP address; all devices connected to the network are assigned unique static IP addresses.
The Time Capsules randomly add IP addresses. Often the Time Capsule will have the assigned static IP address and two other unique IP addresses. It is truly a random occurrence. Sometimes there is only the assigned static IP address and then one or two additional IP addresses will be discovered to have been taken by the Time Capsule. Sometimes this occurs on only one unit and then it will occur on both. When the random IP address duplicates an assigned IP address for another device on the network, then the inevitable network address conflict error causes problems for the device operation.
I have reset each unit in an attempt to solve the problem, but the random attaching of IP addresses continues.