the storm from the last week tooks me the half of my house roof, a lot of work over the weekend
i take a look into the code and into the database. if i add a new item, doesn't matter, what single shop i use, make's a entry in the database, table mod_bakery_orders and change the stock for this item in table mod_bakery_items
you dont use the stock and also not the SKU (article number), so it is not possible to change this stock, because, your value (empty in database) is not a numeric value.
For this Case, the script in view.php has a switch (~ line 360) ->// Case: No out of stock orders
the quantity in the basket com's from the form, if you update the basket. the script read's the quantity from the table mod_bakery_orders and calculate the difference to the submitted quantity (zero) from the basket, but you dont have any quantity, but only if the difference is short by stock, the script update the basket
my recommendation: use a stock for all items. its possible, to set this stock for every item to a number with 20 letters like 10.000.000.000.000.
000.000, i use (in the most cases) a number with 100.000 (without Point - numeric format) and check this from time to time. maybe it's important for the shop owner, that nobody buy this article, if not avaiable in the stock in reality, but also possible, that all items every time avaiable (for the next 10 years), but then use a high value for the stock, like a million or more, doesn't matter, but enough for the next 10 years.
From my point of view, the stock is important for the calculation of everything.
P.S.: single shop or multiple shop's like your has nothing to do with the problem, important for the Order is only the order-id and this works with a session, unique for every visitor
the link to the basket must go to one of the shop-pages like buketi.php, it doesn't matter, what shop - it was wrong in my last post, because, i use a different construct in my test area - sorry for trouble
if it's not work with a stock and you have the same problems, pls check the database table mod_bakery_orders before and after you delete a item in the basket. Maybe, we've to look in this code in view.php ~ln 360 ff and add some control output's, what the script does or not