This is because conflict of Bootstrap 2 & 3. it is basically issue with templates BUT we are working on this to find some solution these modals can work independently without getting effected by templates styles.
We are releasing new version this week. We have escalated your issue and will definitely address a fix in upcoming version.
Every client & query is very very important for us, so hold tight our support team is working on emergency scale on this.
Thanks for the reply, please visit https://winlinesolutions.com/shop/product-category and below category 1 product is there, click on Qucik View or Add to Cart buttons, see what is happening. Page will stuck there only.