Is Stripe.js supposed to catch ALL errors that may occur? - ruby-on-rails

Question

Users can subscribe to my Rails app through Stripe:
class Subscription::CreditCardController < Subscription::PaymentController
def new
stripe_customer = Customers::FindOrCreate.call(current_account)
if stripe_customer
#stripe_subscription = Subscriptions::Create.call(current_account, #price, :payment_behavior => "default_incomplete")
#client_secret = #stripe_subscription.latest_invoice.payment_intent.client_secret
else
flash[:notice] = "An error occurred."
redirect_to plans_path
end
end
def create
flash[:success] = "Subscription created."
redirect_to plans_path
end
end
I am relying on Stripe.js to catch any errors that may occur:
form.addEventListener('submit', function(e) {
e.preventDefault();
handlePayment();
});
function handlePayment() {
stripe.confirmCardPayment(clientSecret.value, {
payment_method: {
card: card,
billing_details: {
name: name.value,
email: email.value
}
}
}).then(function(result) {
if (result.error) {
displayError(result.error);
} else {
form.submit();
}
});
}
This works in 99 % of all test cases so far. Stripe.js catches pretty much every error that can possibly occur. But on some rare occasions it does NOT, so that the error occurs on the server when Stripe is trying to create the Subscription, leaving it in an incomplete state.
This is a major problem because I am not handling these type of errors in my create controller action right now.
So why is it that Stripe catches most of these errors but not all? As a developer, am I supposed to validate user input with Stripe.js AND on the server? Or will one of the two suffice? Reading through Stripe's documentation I was under the impression that Stripe.js will handle everything for me and that I won't have to add additional checks on the server level.
Is this not correct?