Reassign Case Role Not Working in 4.7
Ok I see your config is still on the demo. A key piece of information missing is that the new relationship type is defined for a different type of contact (Student) than the client. If I change the relationship type to be between Individuals it works fine.

The role is a relationship with the CLIENT. If the client is an Individual, the relationship type needs to be one that is also with an Individual.

You could argue it would be nice to have an error popup, but this just seems like a configuration issue - it needs to be the same type as the client.