Same VM added multiple times in VM list

I recently noticed that the number of VMs in Observium was increasing. When I pulled up the VMware host's device page, I saw that the same VM is being detected as a new VM every few hours. I'm guessing its doing this at every discovery run every 6 hrs? Is it because Observium tracks VM using some unique ID returned by VMware and VMware sends a new ID each time? Even then, the old instance of the VM should be deleted, right?