Review Stars showing with no reviews on product

We have previously used Stamped.io for our product reviews, but recently uninstalled the app and went with the native Shopify app.

However, it has left some products displaying reviews that just don’t exist anymore. See example below:

https://www.rugbystuff.com/products/stampede-pro-sg-rugby-boots-deep-ocean-blue

We’ve had a look at the code, and can’t seem to find any way to hide this displaying.

The other problem is that duplicating the product also causes the new product to also display these reviews, even although they are brand new products.

Can anyone help?