Q. Why does the child OS lose its static-IP configuration when I move virtual machines (VMs) between Hyper-V servers?

A. If you move VMs between multiple Hyper-V server hosts or a cluster of Hyper-V server hosts, you need to ensure that the virtual networks have the same name on every Hyper-V server. If the virtual networks don't have the same name when you move a VM from one Hyper-V server to another, the VM might not connect to any virtual network and as a result, the VM would completely lose connectivity. If the VM fails to connect to a virtual network and loses connectivity, you'll get an error message stating that the virtual network doesn't exist.

Naming virtual networks the same on all your Hyper-V hosts should correct your problem. If a VM has defined a static MAC address, then the static MAC address should also be preserved when you move the VM between virtual hosts.