On the cart display page, i added a second binding for charter, you should delete the second binding.
also delete the var dump code i added at the end of the page before the closing </body> tag:
<pre><?php var_dump($_SESSION); ?></pre>
to get the charter working on the KP60 page, i had to double click the add to cart button behavior, then click ok to regenerate the code, try that on the other pages as well.