Lineitems duplicated in cart

[nsaeed]

when add item to the cart and update the quantity it create 2 line items with same everything except it split the quantity on it so if i added 3 first 1 quantity will be 2 and the other will be 1 and if i added 1 more then first will have quantity 2 and other 2 please fix this issue as soon as possible we have issue in our cart

i use the api to add cart items