Problem?

That´s not a problem but a blessing as reviewgolf said.

Why do you want 2 domains with the same content? There is no benefit in that. Lose one domain and continue with the other.

The 301 redirect is the way to go. Then simply try to contact webmasters that link to the redirected domain and ask them to change the link. Of course you will lose some backlinks, but in total you will win. Leave the 301 redirect up untill you´re confident that the site can continue on its own. (that could take as long as a year.)

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