Magento2 : Configurable products are not updating in cart

Question

I have configurable product in my store and I am using magento2.2.6.

When I edit the product from cart page and Mini Cart, it not update the product, it added the new product in the cart, Some time it updating the product but most of the time it add other product with same variation.

Process to replicate this issue:-

• Add any configurable product in cart with size "X".
• Now click on edit icon for this product and select "XL" and click on update cart button.
• It should update the same product size from "X" to "XL".

but it added the product as duplicate as shown in above image.

Please suggest me the solution to fix this.