vCenter server is restored to the snapshot when it recognized virtual machine as template, but the template has already been converted to virtual machine actually.
Timeline of occurrence 1. Convert VM to template. 2. Take snapshot of vCenter Server. 3. Convert template to VM. 4. Restore snapshot of vCenter Server taken at Step2. 5. The virtual machine and template appear with the same name on vSphere Client, and the problematic behavior can be reproduced.
Resolution
To reflect the actual state of the virtual machine, delete the template from the inventory.