Unauthorized error using Stripe/PayPal Advanced Processing in other currencies

We are getting regular errors when users in different to default currencies try paying by card using Stripe/PayPal advanced processing. We have tried tweaking how currencies load on the checkout with no luck. We use Kinsta for hosting which has caching too. The site is https://funkmotorsport.com

In summary:

– if a customer pays in GBP via card through Stripe or PayPal Advanced Processing (SUCCESS, no issues)
– if a customer pays in GBP via PayPal (SUCCESS, no issues)
– if a customers pays in any other currency besides GBP and pays by card – Stripe or PayPal Advanced Processing (FAILURE – ‘UNAUTHORIZED)
– if a customer pays in any currency besides GBP and pays via PayPal (SUCCESS – no issues)

Feel free to set up a free product etc to help with testing!