Menu bottom page

After a few days working on the theme, I’ve seen that the navbar menu appears twice: first of all in the header of the page, and second at the bottom of the page, after the footer. I’ve been trying to find the problem and it seems that the wp_nav_menu method generates the menu twice, but I can’t find out why. The menu in the navbar has all the css style features, but when it’s generated on the footer, it appears in html format view (a list).

Any ideas of what could be generating this error?

Thanks