Shipping Pricing Problem

[diana_lozada]

Hi I manage a fashion store, we want to open the store soon but we've been having a problem with the carriers pricing. When you add an item to the cart it has a cost and it adds it correctly but when you add 10 to 13 items the pricing frozes, like it costs the same but it doesn't, and when you add 14 it charges the correct price for shipping again. I've tried modifying the carrier, the cache but nothing, I even created a local store but it happens in there too so I don't know if is a bug or if I'm doing something wrong when creating the carrier. I've been having this problem for a month now and haven't been able to figure out what could be causing the problem. Does anyone have an idea of what could be causing this problem? This is the store address, is build in prestashop 1.6