Facebook Graph API /inbox endpoint returning incomplete response

Question

I have built a desktop application that makes use of the FB graph api enpoint /me/inbox. (also using the Facebook C# SDK 5.4.1)

As of May 31st I have noticed that the responses from this FB API are incomplete. There is missing information from each message within the reponse; The initial sender of the message (creator of the initial message in the thread) is no longer present. The following is missing

        "from": {
            "name": "....",
            "id": "..."
        },

And the "message" text is also missing. "message": ".....",

A typical (good) message looked like this:

{
       "id": "....",
        "from": {
            "name": "....",
            "id": "..."
        },
        "to": {
            "data": [
                {
                    "name": "...",
                    "id": "...."
                },
                {
                    "name": "....",
                    "id": "..."
                }
            ]
        },
        "message": ".....",
        "updated_time": "....",
        "unread": 0,
        "unseen": 0
 },

Is anyone else experiencing this issue?