Okay, so update from this end – having been experimenting to try and narrow this down, it appears to be related to the quantity of a product. If the quantity involves a decimal (eg 1.5kg of something ordered which is sold by the kg), then there’s a javascript validation error:
An invalid form control with name=’order_item_qty[8109]’ is not focusable. <input type=?”number” step=?”1″ min=?”0″ autocomplete=?”off” name=?”order_item_qty[8109]?” placeholder=?”0″ value=?”1.5″ data-qty=?”1.5″ size=?”4″ class=?”quantity”>?
(Plugin All in One Product Quantity for WooCommerce is installed, however this is set to allow decimal quantities.)
