Help- Duck confit undershot - can it get a second round of sous vide after cooling?

Spent a small fortune on ducks. I get them butchered and do the whole shebang... breasts, confit, liquid gold, stock, etc... I was in a rush and despite a beautiful brine for the confit with star anise, salt, sugar, orange, cinnamon, herbs; I undershot the cook time because I was impatient and in a huge rush. The confit was Sous vide for only 12 hours ( my usual is 17 - 20)

I now have delicious meat that is tough and stringy. This has never happened before and my temp was consistent with past efforts. It's been ice chilled and refrigerated for a few days. Can I pop it back in the sous vide for additional hours to make up the difference or am I at risk of killing someone?!

If not, perhaps someone has a solution for this tenderizing this yummy meat... Please, help! Galgoneglutenfree.com