Politico has published a very different view of the use of the GFA as a way of resolving the impasse.

UK to warn of Brexit backstop's threat to Irish peace treaty

The detail is beyond my understanding, but the (UK) argument seems to be that the WA as it stands conflicts with the provisions of the GFA.

It follows accusations from DUP MPs and other leading unionists that the backstop itself contradicts the very historic peace agreement that it is designed to protect.

I'll leave others to comment if it is thought worthwhile to do so.