“You must add a minimum…” On first click only

First of all, thanks for a very useful plugin.

I have one issue that I need some help with…

When I try to add a product to the cart the first time it always says “You must add a minimum of 12 items…” But the lowest amount is set to 12, wich is also showing.
As soon as i click the amount-button once the problem is solved. Even if im increasing the amount to 24 and then go back to 12.

Any ideas on how to solve this?

Big thanks for any help!