For me it only seems to happen if I remove or replace anything that has a large visible circuit board attached to it or would have a visible circuit board attached it if was not virtual (IE: network cards, motherboards, graphics cards). I have been able to increase disk size, add disks, memory, and CPU cores without any issue dozens of times. Just make sure you use showhwpf in the /Server directory to capture your hardware profile first, since you don't want to lose it if anything happens.