Error Messages When Adding Products to Cart (Cannot read properties of null - reading 'classList')

[oldadamfield]

Hi there

We have an issue where we have products with lots of inventory but when the product is added to the cart a message appears saying 'Quantity selected exceeds current stock'. However, at this point, the items are still added to the basket, see this video: https://www.loom.com/share/6ca83f5d26f04accb0365eea08c0a50f?sid=ec1c61b5-68a7-4d5d-8699-8445d7c45b0e

A similar message appears when using the 'Quick Add' to cart feature, when adding an item the following error occurs "Cannot read properties of null (reading 'classList')". Again the products are still added to the cart, see the video: https://www.loom.com/share/f010cb602bd24aa4a209281e66c3ca5c?sid=b49dc358-fd8b-4ee5-9c6b-496510fe8d42

Here is the site which is currently not password protected: https://8b6bf4-2.myshopify.com/

Thanks for your help.

Adam