Symptoms:
If you have force stopped a VM replication from local site (outgoing), but not the corresponding replication on the remote site (incoming) then you will get an error message mentioned below & won't be able to re-add this VM to replication.
ERROR
Operation Failed
Unable to configure replication for virtual machine 'virtual machine' because group 'virtual machine' cannot be created. Another virtual machine 'virtual machine' that has the same instance UUID '50206a21-####-####-####-##########b2' already exists on protection site '(Protected Site)'.
Operation ID: c4eb75b7-####-####-####-##########a6