Weird Products URL

I have encountered a few problems with my product URLs. I am not sure if this has to do with the theme, plugins or anything like this but I would really appreciate your help.

So basically, in my google search console I have nearly all of my URLs as not found (404 error). Now, the pages exist as I can access them via my website but the URL look different.

For example, the URL for this product is: http://www.boxofsquares.com/product/visual-philosophy-retro-architecture-poster/ and in Google Search console this has the 404 error along with other similar product links like this.

Now, when I click on the error to see details, it says that the URL is linked from http://www.boxofsquares.com/product/visual-philosophy-retro-architecture-poster/ to http://www.boxofsquares.com/product/visual-philosophy-retro-architecture-poster/www.boxofsquares.com

So the URL has my sitelink added at the end of it for some reason. Can you please advise me on what I should do to rectify this?

I have checked my plugin Yoast SEO and under the Search Console tab, all of the product URL have the sitelink at the end and I have never added it there.

Please let me know what this could be.

Regards,

Marius