Problem with second billing address on checkout

-- HikaShop version -- : 2.6.3
-- Joomla version -- : 3.6.0
-- PHP version -- : 5.5.30
-- Error-message(debug-mod must be tuned on) -- : HTML
403
Error: 403
Access forbidden.

Console:
"NetworkError: 403 Access forbidden. - http://localhost/joomla/hikashop-menu-for-categories-listing/address/save/subtask-TYPE/cid-0/fid-hikashop_checkout_-TYPE-_address_zone/tmpl-component"

Hi there,

I get the error message I reported when raising this post
HTML
403
Error: 403
Access forbidden.

Console:
"NetworkError: 403 Access forbidden. - http://localhost/joomla/hikashop-menu-for-categories-listing/address/save/subtask-TYPE/cid-0/fid-hikashop_checkout_-TYPE-_address_zone/tmpl-component"

this happens when a user submits a second billing address on the checkout. that is, below the first billing address it clicks on new, completes the form with the second billing address and then clicks on the "tick" icon to submit the new billing address.

In the configuration I have selected "address selector" = list. If I select "popup" the error does not happen. But I want to use the "list" option. Can you replicate the error?

thanks

OK, the error disappears if I disable sh404SEF...

it looks like Hikashop is not compatible with sh404SEF since I have other issues when creating Hikashop menu items which become unroutable with sh404SEF enabled

...is there any solution/plugin to integrate sh404SEF and Hikashop?

I see another issue with Billing Addresses ( with sh404SEF disabled). I can create a new Billing Address ("address selector" = list) on the checkout process but when deleting this new Billing Address (the one I just created in the checkout process by clicking on the bin icon), this address is removed from the database but it does not disappear from the checkout view. Only billing addresses that were in the database before the checkout process started would disappear from the checkout view when deleted. Can you replicate?