Noticing you cannot go to payment_failed if you have removed the confirm step: https://github.com/solidusio/solidus/blob/main/core/lib/spree/core/state_machines/order.rb#L81

We had this issue as well. Weirdly, it seems to only raise an error the first time it attempts to transition an order to payment_failed. Our messy fix was to rescue the order.complete call, then let the user be redirected to the payment step with a payment unsuccessful flash. I'm interested, have you found a more straightforward solution?