Pricing Issue while customer re-login.

Once customer login and add products to the cart, from the cart page we have given facility to break the product(same products) into multiple line items based on the delivery date requested by customer.

Example: Say customer added 40 mobile phones in cart. He wants 10 products to deliver on 10/02/2019 and 30 products on 10/03/2019. Here we have given link to the cart page to select the date and on the basis of that we are splitting the cart entry on having the quantity as 10 and other 30. Here we have also done customization to apply volume price on total quantity for the products (40) instead of product line items. And it working fine till.

Price structure for product A is like below. 1-10 :$456 11-50:$427

Now issue is when customer logout and login again after selecting two delivery date ,the price is getting changed according to product line level quantity. Please refer to the attachment for more clarity. Any help is highly appreciated.link text