We are going through something similiar.
My husband has a child, and on the application we idenfied that the son is non-accompanying.
We also explained in the original application, that we have attempted to contact the mother to obtain medicals for the son, with no success.
After getting our AOR, he received a notice for additional documents.....medicals for his son.

My husband found where the mother and son was living. He drove 16 hours there......and got prior advice to try and go there and see if the mother would be resonable, after all he wants to have a relationship with his son but the mother has been very evasive and not provided him with any access.
Long story short, he went. She yelled and screamed. He called the police (to document this). The son was there, but the mother refused to allow him to see his son. The police said it there wasn't anything they could do, they couldn't force the child to come out or allow the mother to release the son. They suggested that he file a court order stating that the mother is denying him access at the local courthouse. He filed the documents at the courthouse.
The mother is trying to change the son's last name (crazy).
They have a court date to establish visitation. My husband has hired a lawyer for this.
We haven't been successful in getting the medicals, and not sure if or when we will. In lieu of this, we have provided the court papers that he has filed which specfies that he is attempting to have access to his son, but the mother is refusing this.
We also wrote a detailed letter of what we have gone through, to try and get the medicals. We got this notarized and also submitted this. The letter says that he will NEVER attempt to sponsor his son to come to Canada, and to please continue processing the application.
We are hoping and praying this will suffice. We don't have any other options or a back-up plan. All our eggs are in this basket.
All we can hope for is that Buffalo will see our efforts and show compassion.