Probable cause:
- Ajax/ Drawer Cart
- Any other sales channel other than Shopify product page like Facebook or any remarketing/retargeting tools/apps that bypass Shopify product page like Permalinks to pre-load the cart
- Third-party product option apps that use ajax
- Upsell apps
- Lazy loading
- A quick view in the collection page or similar product list or recently visited product list
- Additional Popup Add to cart button