Facebook Graph API "/{page-id}/feed" is not working with App Access Token

We are facing issues with Graph API. The Facebook Graph API "/{page-id}/feed" is not working for all pages with a valid App Access Token. Previously it used to work. We noticed it today the API is throwing error

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{ "error": { "message": "An unknown error has occurred.", "type": "OAuthException", "code": 1 } }

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Not working pages:

http://ift.tt/1AV6yoY http://ift.tt/17Bo6IN

Note: And its working if we pass a User Access token instead of App Token.

Facebook developer Docs says "An access token is required to view publicly shared posts." So App Access Token should work!

Does Facebook change something inside the API?. Can any one help to solve the issue