You know, you just jogged my memory here. We did have an issue with Stripe changing the order / timing of payment_failed webhooks, which caused them to be sent

You know, you just jogged my memory here. We did have an issue with Stripe changing the order / timing of payment_failed webhooks, which caused them to be sent before the next payment attempt was known. We used the payment failed hook to send an email to our customers and let them know when we'd be retrying the charge, which was no longer possible because the next_payment_attempt field was null. Before the change, a next_payment_attempt=null meant the charge would not be retried. I reported the issue and the webhook changes were rolled back a month later. Really threw a wrench into our flow. I will say that generally speaking, Stripe is the canonical backwards compatibility API in my mind. With a few edge cases.