That's normal. If you boot the replicated VMs, then blocks will be changed. It mean no further delta replication will work on this VM. Force boot it if you lost the original VM and you don't care about delta toward the copy anymore. If you just want to test the VM without doing a new full (breaking the delta chain), boot with a copy. I think I explained that in this video: https://www.youtube.com/watch?v=FfUqIwT8KzI
That's a display glitch.