Free Gifts for WooCommerce

I work for a company and my colleague bought the Free Gifts for Woocommerce plugin. At first it worked great, but there may be a limitation on the products ID. I want to add a Free Product with a higher ID (in our case 11350) – unfortunately that doesn’t work. If I add a product with ID up to 4999, it works fine. So I assume that all products that have an ID higher than 5000 can no longer be added.