Race condition Stripe signup

[FelixMalfait]

I tried to signup today with a credit card but after being redirected I saw the page telling me to pick a plan again, probably because the webhook hadn't arrived yet. Then I clicked to pick the plan, when back to Stripe's billing page, when back to the previous page with the browser, then saw the "Payment success" page.

I would guess there is a race condition if we redirect before the Stripe webhook has arrived then the "pick a plan" modal is being displayed? We shouldn't display it on the Payment success page.