Locale at checkout is always showing "en", but should change

[KlaudiaZapiet]

Hey Shopify community!

I've been experiencing locale issues on this store https://mimiandaugust.com/

1. Add any item to your cart

2. On the cart page, select store pickup

3. Proceed to checkout

In the form action, I can see that our app is setting the locale as en-GB, however at checkout, the URL always shows locale=en 

Here's the checkout URL: https://mimiandaugust.com/checkouts/c/fa49b8c738daf2f3f93245da9c215f8b/information?discount=+&locale...

If I test it out using Online Store > Themes > Customize, I see the correct locale loading. Does anyone know why this is happening and how to solve it?

Any input will be appreciated. Thanks in advance!

[lderome2]

Hi - Have the exact same issue... did you find the problem ?

Thank you 

[LuckyLuc]

Having the same issue here too!