[trevorhinesley]

I don't see the payment intent endpoint listed here, which means you're not allowing for authentication challenges (SCA/PSD2). So it's possible the bank is denying the charge, but your flow isn't accounting for it if it's not using payment intents. See here for updating your implementation to account for SCA: https://stripe.com/docs/strong-customer-authentication/migra...

[sunaurus]

This was my first thought as well. OP, your symptoms sound very similar to an app I recently updated to support SCA - it was just dropping a portion of the payments.