There isn’t a built-in option to exclude a CSS class from the theme’s lazy loader. The recommended way is to disable lazy loading only on the specific page where it breaks images, using a Theme Settings preset.
Steps:
1) Dashboard > WoodMart > Theme Settings > Theme Settings presets > Add new preset.
2) Add a rule that targets your FunnelKit Thank You (order confirmation) page. If the plugin provides a dedicated page, select that page. If not, target the WooCommerce “Order received” page/endpoint used after checkout.
3) Save the conditions.
4) Open the preset settings, go to Performance, and turn off Lazy loading for images (and for background images if needed).
5) Save and clear caches, then test the order confirmation page again.