I've noticed a problem with Cart API update. It happens sometimes, but not all the time.
We are headless. And using graphQL storefront API to update the cart. Usually, all good, but several days ago I noticed that customers complaining, that cart is not allowing to have more than 1 item.
I did some debugging and I found that when you want to add a second item to the cart, API returns a new cart with a new id but with the requested item. So it looks like you're replacing the current line item, but not applying the second one.
The only way I found to "fix" it is just to delete the current cart id and create a new cart. A new cart does not have such an issue. Is there a normal way to fix it?
I heard, that people on rest API also facing this problem.
In a few words: Cart does not reuse existing cart id, but creates a new cart instead. For example: I requested to add the item to the card with id 123, in response I'm getting a cart with id 456 with only one item, which was requested to be added to the cart with id 123.