Cart quantity randomly changing at checkout

[Abbab]

Hello, 

I've been having some trouble recently on my website. I've updated the cart code to group products by vendors when the items are added in the cart by the customers. Everything works correctly for the grouping function. But I've noticed that the quantities of the items in the cart page are randomly changing when I proceed to checkout. For example, if the first item in the cart have a quantity of 5 and the third item have a quantity of 8, when I proceed to checkout the quantities are randomly assigned to other cart items meaning that what the customer ordered at the beginning is totally different at checkout.

It's really weird so I'm not sure why the quantities are randomly changing at checkout. I've added the link of my preview store : https://1y71mwtj03jswtaz-22604799.shopifypreview.com  

What should I do to solve this problem ?

Thank you very much !

[vladf9]

I have the exact same issue. What was the solution for you in the end?