2 Products are added instead of just one

Hello,

I use the plug in ‘Fancy Product Designer’ to let my customers make their own shirt designs. However, I noticed that when the customer adds a new customized shirt, it adds 2 products to the cart – the original sample shirt, as well as the one that he customized. I noticed that when I turn off Woocommerce Boost Sale plugin, this doesn’t happen. It’s only when I switch on Woocommerce Boost sale plug in that I notice this issue happening.

Please see what I mean from this link:

http://tinyurl.com/y688p43j

Please advise.