Products on the cart disappeared when user add more than 40 products

Steps

1. Open https://uat.mec.ca/en/
2. Tap on menu > click on men
3. Click on footwear > sandals
4. Click on “Brikenstock boston leather”
5. Chose size 38,change quantity to 20 and click on “add to cart “
6. Click on “X” at the top and add another 20 into the cart
7. Repeat step 6 and observe

Actual result

When user was adding products to the cart 20 by 20 and when he arrives is 40 items and add again 20 items , products on the cart disappears

Expected result

User expect products to not disappear from the cart or a message there are no available items in this quantity should displayed