I have a vm with a vm_name example in the folder vagrant-templates, but when I try to create another one with the same vm_name inside the empty folder vagrant-templates/packer, packer 1.4.0 with vsphere-iso v2.3 refuses to start with:

example already exists, you can use -force flag to destroy it: <nil>

This is a bug that should be fixed by making sure vm_name is only unique within the folder and not the entire cluster.