This post was very helpful:https://community.shopify.com/c/shopify-discussions/unable-to-debug-quot-there-was-an-error-while-updating-your-cart/m-p/1098610

Hi @Don Also I reverted the cart-template.liquid file back to the original and I'm still having the problem.Andy

Hi DonI've rolled back to the earliest version of cart-template.liquid.I've customised the product page to accept a custom value (a personalised note), which functions elsewhere as expected.  I did follow the article you referenced but there is one l...

HiWe are running a Shopify site with the Debut theme which we've customised.  https://littlecashmerecompany.co.uk/Users can add and checkout single products fine.When a user goes to the cart and updates a single product to multiples (doesn't matter f...