WEIRD (!!) Bug: Only with 2 items - this error message: The product selection cannot be delivered by the available carrier(s): it is too heavy. Please amend your cart to lower its weight.

[BabsD]

Hi, 

I am looking for help because I can't figure out why this WEIRD bug is driving me crazy!

I have a couple of products on our website which can't get checked out if there are 2 of them in the cart. As soon as I do one or 3 or more, it works, but not for 2. 

as an example, try to checkout 2 of these products https://www.zotterusa.com/gifts-and-accessories/572-set-labooko-dark-milk-low-sugar-in-cream-white-gift-box-000000080054.html
with this address
Test Test
33 Spencer Brooks Road
Concord, Massachusetts 01742
United States

It happens to all of the 3 bar sets you can see under new on the home page: www.zotterusa.com

And it only happens with 2 of those products in the cart an nothing else. As soon as I am adding only one or 3 or any other product, it works. What crazy bug could that be?

Thanks a lot for looking into this!

attached are screenshots of the product settings and shipping settings

 

I have 2 more shipping options for a few specific products which are set to a high weight and come with free shipping, but that shouldn't bother the products where it happens

attached those screenshots to show all 4 specified shipping settings