Hi Jerome,
thanks for your help, I will proceed to re-explain the problem in a different way to try to make it simpler:
We have a test site with a clean install of HikaShop, Hikamarket multivendor and latest Joomla.
I have users A, B and C, all them have their own Hikashop client addresses, one for billing, one for shipping.
I enter the site as a Hikamarket Vendor and get in the order administration area.
There I click an order from the list of orders.
I can see the customer who made the order. The selected Billing address. The selected Shipping address.
Under customer section I am allowed to change the user who made the order.
I do.
There is no save button but I know that after changing the user who made the order this gets changed 'on the fly'.
But ATTENTION! Addresses do not get changed!
They are still the former user addresses, so if I proceed with the cart workflow, both the invoice and the shipping label will be emitted to the original user of the order.
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I think that after you change the user who owns the order both adresses should get reseted to nothing or to the new user in charge of the order default address.
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Hope this way is clearer.
Best regards,