1) Empty cart
2) Go to cart page (/cart)
3) Add a product to cart (for example, using a Cart Link, or with an add to cart button from a block)
4) Ajax Cart block is updated, but cart form is not.
This due Ajax Cart relies in the id #cart-form-pane to locate cart form, but Ubecart doesn't add this id when showing an empty cart form (no form is shown at all).