When adding a product it ads it twice?

Hello,

When I add a product using the upsell option it adds the product 2 times, for example if you go to https://www.test.7daysperformance.co.uk/product/impreza-type-r/ and pick any variation then add it to the cart the first time it may do it correct, however, if you empty the cart and re-do this process and add a product variation to the cart yes to the upsell the Subaru is added 2 times and upsell once meaning its wrong, the Subaru only should be added once upsell on top.

Can you see why this is happening? This is on a test site so not on the actual live site as I can’t have customers seeing this,

Thanks,
Matt