@SchroedsBiz@Shopify Resolved this for clients today the submit input requires a value of "Checkout", Shopify have added additional server side validation. If you add this the "/cart" action will work with quantity amends, submissions to checkout etc. Shopify shouldn't be adding this without warning
London, that was magic. Our biggest show yet, 45 thousand of you - all singing songs I wrote in my joggers in me mam’s flat. Wanna say a massive thanks to all our friends who played and made it what it was, absolute joy. Love you all ❤️