In modern, 9.0+, versions of SA, if the UUID of a managed server changes, we interpret this change to mean that the server being managed was cloned. We reach to this change by cloning the device record in SA and pushing the new mid file and agent crypto to the managed server.
If the UUID change was not a result of a clone of the managed server, then this will result in the old device record going offline, and the managed server assuming the identiy of new device record.
There are several circumstances whereby a VMWare virtual machine's UUID will change. Some of these are not the result of a VM clone. The following VMWare articles describe some of these UUID management issues: