Android Changes the IP Reservation in the Router

I do not understand how this is possible. You assign a static IP configuration on the device, or the device obtains a dynamic configuration from the router, or an APIPA (169.254.x.y) is assigned if no Dhcp server responds. The device is not going to change the router's reservation and is not going to assign itself something else.

If what you say is happening there must be some rogue software running on those devices.