ZIP in checkout is already validation failed at page load
When I open the checkout page the ZIP code field is already validation failed. The field doesn't have a value. It doesn't occur every I open the checkout page.
I noticed this with two different Magento 2 environments. One is version 2.1.0, the other one is 2.0.7. It doesn't matter which theme I'm using, it occurs with the blank theme as well. I'm using Dutch locale.