To reproduce:

1. Create two services - service 1 , 2 (service 1 without any instance, and 2 with any instances)
2. Create a third service , add service 1, 2 to the composition canvas
3. Create a service proxy relationship between the service 1 & 2
4. Certify -> results in Invalid content error

After this any changes to the thirds service results in error - i.e. deleting the relationship / deleting the services from the canvas