Line Item Quantitys change after pressing checkout button

[Erik_Abrio]

Hello, we are using the  Shopify Dawn Theme. The dynamic rendering of updated Items works completely fine and shows correctly like it should. But theres some issue. When i press the Checkout button the quantites of 2 items are always switched. To Check this i fetched the cart.js before and after pressing the checkout button. And getting following results.

Does Somebody know what could cause this issue?